Publications by authors named "Christopher Toon"

48 Publications

Acute generalized exanthematous pustulosis to a novel oral anticoagulant (apixaban).

Ann Allergy Asthma Immunol 2021 Jul 31. Epub 2021 Jul 31.

Immunology Laboratory, New South Wales Health Pathology, Royal North Shore Hospital, Sydney, Australia; Department of Anatomical Pathology, New South Wales Health Pathology, Royal North Shore Hospital, Sydney, Australia.

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http://dx.doi.org/10.1016/j.anai.2021.07.022DOI Listing
July 2021

Peri-ureteric mass an unusual case of immunoglobin G4-related disease (IgG4-RD).

Urol Case Rep 2021 Sep 31;38:101666. Epub 2021 Mar 31.

Department of Urology, Royal North Shore Hospital, Sydney, Australia.

Immunoglobulin G4-related disease (IgG4-RD) of the ureter is a rarely reported disease, often mimicking urothelial carcinoma. This paper describes a case of an otherwise healthy patient with a lesion involving the ureter revealed on Computed tomography (CT), avid on fludeoxyglucose positron emission tomography (FDG PET), that prior to surgery was suspicious for urothelial carcinoma, until intra-op frozen section revealed otherwise. Diagnosis of ureteral IgG4-RD should be considered as a differential diagnosis, with serum IgG4 levels obtained.
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http://dx.doi.org/10.1016/j.eucr.2021.101666DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8058513PMC
September 2021

Patterns of p53 immunoreactivity in non-neoplastic and neoplastic Barrett's mucosa of the oesophagus: in-depth evaluation in endoscopic mucosal resections.

Pathology 2019 Apr 28;51(3):253-260. Epub 2019 Feb 28.

PathWest Laboratory Medicine, Perth, WA, Australia; School of Pathology and Laboratory Medicine, University of Western Australia, Perth, WA, Australia.

There is increasing interest in p53 immunohistochemistry as an adjunct to haematoxylin and eosin (H&E) assessment for dysplasia in oesophageal Barrett's mucosa; however, published information on the patterns of staining remains scant. Here, we present descriptions of normal and aberrant p53 staining in non-neoplastic and dysplastic Barrett's mucosa in endoscopic mucosal resections. A retrospective series of archival endoscopic mucosal resections for biopsy proven dysplasia at our institution were retrieved for this study, comprising 28 sections from 23 patients. p53 immunohistochemistry was performed using an in-house optimised protocol and the staining pattern assessed in H&E confirmed non-neoplastic, dysplastic and neoplastic areas of Barrett's mucosa with regard to individual cell intensity and location of positive cells with respect to gland microanatomy. In non-neoplastic epithelium, normal p53 staining was weak, heterogenous and localised to the crypts. In dysplastic epithelium, p53 over-expression was seen which was of moderate to strong intensity in either a crypt predominant location or diffuse involving crypt and surface epithelium. The crypt predominant pattern was observed more commonly in low grade dysplasia while the diffuse pattern was more commonly seen in high grade dysplasia. In a minority of cases, there was complete loss of p53 staining in dysplastic epithelium and contiguous neoplasia (null phenotype). p53 immuno-expression in non-neoplastic and dysplastic Barrett's mucosa is distinctive when interpreted with regard to cell intensity and gland microanatomy. We propose that these staining patterns may assist in the interpretation of dysplasia in endoscopic biopsies of Barrett's mucosa.
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http://dx.doi.org/10.1016/j.pathol.2018.12.415DOI Listing
April 2019

NK-cell enteropathy, a potential diagnostic pitfall of intestinal lymphoproliferative disease.

Pathology 2019 04 26;51(3):338-340. Epub 2019 Feb 26.

Sydney Medical School, University of Sydney, NSW, Australia; Tissue Pathology and Diagnostic Oncology, ICPMR, Westmead Hospital, NSW, Australia.

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http://dx.doi.org/10.1016/j.pathol.2018.09.064DOI Listing
April 2019

Extracellular Vesicles from Neurosurgical Aspirates Identifies Chaperonin Containing TCP1 Subunit 6A as a Potential Glioblastoma Biomarker with Prognostic Significance.

Proteomics 2019 01;19(1-2):e1800157

Brainstorm Brain Cancer Research, Brain and Mind Centre, University of Sydney, NSW, Australia.

Glioblastoma, WHO-grade IV glioma, carries a dismal prognosis owing to its infiltrative growth and limited treatment options. Glioblastoma-derived extracellular vesicles (EVs; 30-1000 nm membranous particles) influence the microenvironment to mediate tumor aggressiveness and carry oncogenic cargo across the blood-brain barrier into the circulation. As such, EVs are biomarker reservoirs with enormous potential for assessing glioblastoma tumors in situ. Neurosurgical aspirates are rich sources of EVs, isolated directly from glioma microenvironments. EV proteomes enriched from glioblastoma (n = 15) and glioma grade II-III (n = 7) aspirates are compared and 298 differentially-abundant proteins (p-value < 0.00496) are identified using quantitative LC-MS/MS. Along with previously reported glioblastoma-associated biomarkers, levels of all eight subunits of the key molecular chaperone, T-complex protein 1 Ring complex (TRiC), are higher in glioblastoma-EVs, including CCT2, CCT3, CCT5, CCT6A, CCT7, and TCP1 (p < 0.00496). Analogous increases in TRiC transcript levels and DNA copy numbers are detected in silico; CCT6A has the greatest induction of expression and amplification in glioblastoma and shows a negative association with survival (p = 0.006). CCT6A is co-localized with EGFR at 7p11.2, with a strong tendency for co-amplification (p < 0.001). Immunohistochemistry corroborates the CCT6A proteomics measurements and indicated a potential link between EGFR and CCT6A tissue expression. Putative EV-biomarkers described here should be further assessed in peripheral blood.
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http://dx.doi.org/10.1002/pmic.201800157DOI Listing
January 2019

Parafibromin-deficient (HPT-JT Type, CDC73 Mutated) Parathyroid Tumors Demonstrate Distinctive Morphologic Features.

Am J Surg Pathol 2019 01;43(1):35-46

Sydney Medical School, University of Sydney, Sydney.

The gene CDC73 (previously known as HRPT2) encodes the protein parafibromin. Biallelic mutation of CDC73 is strongly associated with malignancy in parathyroid tumors. Heterozygous germline mutations cause hyperparathyroidism jaw tumor syndrome,which is associated with a high life-time risk of parathyroid carcinoma. Therefore loss of parafibromin expression by immunohistochemistry may triage genetic testing for hyperparathyroidism jaw tumor syndrome and be associated with malignant behavior in atypical parathyroid tumors. We share our experience that parafibromin-negative parathyroid tumors show distinctive morphology. We searched our institutional database for parathyroid tumors demonstrating complete loss of nuclear expression of parafibromin with internal positive controls. Forty-three parafibromin-negative tumors from 40 (5.1%) of 789 patients undergoing immunohistochemistry were identified. Thirty-three (77%) were external consultation cases; the estimated incidence in unselected tumors was 0.19%. Sixteen (37.2%) fulfilled World Health Organization 2017 criteria for parathyroid carcinoma and 63% had serum calcium greater than 3mmol/L. One of 27 (3.7%) noninvasive but parafibromin-negative tumors subsequently metastasized. Parafibromin-negative patients were younger (mean, 36 vs. 63 y; P<0.001) and had larger tumors (mean, 3.04 vs. 0.62 g; P<0.001). Not all patients had full testing, but 26 patients had pathogenic CDC73 mutation/deletions confirmed in tumor (n=23) and/or germline (n=16). Parafibromin-negative tumors demonstrated distinctive morphology including extensive sheet-like rather than acinar growth, eosinophilic cytoplasm, nuclear enlargement with distinctive coarse chromatin, perinuclear cytoplasmic clearing, a prominent arborizing vasculature, and, frequently, a thick capsule. Microcystic change was found in 21 (48.8%). In conclusion, there are previously unrecognized morphologic clues to parafibromin loss/CDC73 mutation in parathyroid tumors which, given the association with malignancy and syndromic disease, are important to recognize.
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http://dx.doi.org/10.1097/PAS.0000000000001017DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6296846PMC
January 2019

An unusual presentation of eosinophilic angiocentric fibrosis.

J Surg Case Rep 2017 Dec 8;2017(12):rjx234. Epub 2017 Dec 8.

Department of Otolaryngology, Head and neck surgery, Royal Prince Alfred Hospital, Camperdown NSW, Australia.

Eosinophilic angiocentric fibrosis (EAF) is a rare, benign condition affecting the respiratory mucosa and is generally characterized by a locally destructive growth. We present a case of a lady with a saddle nose deformity that had for many years been treated as granulomatosis with polyangiitis (GPA), of which saddle nose deformity is a classic feature. At the time of surgery, she was found to have subglottic stenosis another classic feature of GPA, however, histology demonstrated EAF. We discuss the difference between the two conditions and highlight the importance of making the correct diagnosis.
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http://dx.doi.org/10.1093/jscr/rjx234DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5723982PMC
December 2017

The epithelioid BAP1-negative and p16-positive phenotype predicts prolonged survival in pleural mesothelioma.

Histopathology 2018 Feb 29;72(3):509-515. Epub 2017 Nov 29.

Cancer Diagnosis and Pathology Group, Kolling Institute of Medical Research, St Leonards, NSW, Australia.

Aims: Mesothelioma is a relatively uncommon but highly malignant neoplasm. Most patients die of disease within 1 year of diagnosis, but some have prolonged survival. Prospective identification of these longer-term survivors may help to guide treatment. We therefore sought to investigate the role of p16 immunohistochemistry (IHC) both alone and in combination with other markers as a potential predictor of prolonged survival in mesothelioma.

Methods And Results: P16 IHC was performed on unselected pleural mesotheliomas biopsied from 1991 to 2014; 153 of 208 (74%) cases were p16-negative, which correlated significantly with poor overall survival in both univariate (median survival 7.6 versus 13.6 months; P = 0.001) and multivariate analysis [hazard ratio (HR): 1.632; 95% confidence interval (CI): 1.103-2.415; P = 0.014]. Other independent factors associated with prolonged survival included loss of expression of BAP1 and epithelioid morphology. We therefore stratified patients further based on these three independent prognostic variables and demonstrated an unusually prolonged survival in mesotheliomas which were epithelioid, BAP1 IHC negative and p16 IHC positive (12% of cases, median survival 31.7 months, P < 0.0001).

Conclusions: In conclusion, p16 IHC is an independent prognostic biomarker in pleural mesothelioma. When used in combination with BAP1 IHC and morphological subtyping, patients with exceptionally prolonged survival can potentially be identified.
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http://dx.doi.org/10.1111/his.13392DOI Listing
February 2018

Whole-genome landscape of pancreatic neuroendocrine tumours.

Nature 2017 03 15;543(7643):65-71. Epub 2017 Feb 15.

QIMR Berghofer Medical Research Institute, Herston Road, Brisbane 4006, Australia.

The diagnosis of pancreatic neuroendocrine tumours (PanNETs) is increasing owing to more sensitive detection methods, and this increase is creating challenges for clinical management. We performed whole-genome sequencing of 102 primary PanNETs and defined the genomic events that characterize their pathogenesis. Here we describe the mutational signatures they harbour, including a deficiency in G:C > T:A base excision repair due to inactivation of MUTYH, which encodes a DNA glycosylase. Clinically sporadic PanNETs contain a larger-than-expected proportion of germline mutations, including previously unreported mutations in the DNA repair genes MUTYH, CHEK2 and BRCA2. Together with mutations in MEN1 and VHL, these mutations occur in 17% of patients. Somatic mutations, including point mutations and gene fusions, were commonly found in genes involved in four main pathways: chromatin remodelling, DNA damage repair, activation of mTOR signalling (including previously undescribed EWSR1 gene fusions), and telomere maintenance. In addition, our gene expression analyses identified a subgroup of tumours associated with hypoxia and HIF signalling.
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http://dx.doi.org/10.1038/nature21063DOI Listing
March 2017

Hypermutation In Pancreatic Cancer.

Gastroenterology 2017 01 15;152(1):68-74.e2. Epub 2016 Nov 15.

QIMR Berghofer Medical Research Institute, Brisbane, Queensland, Australia; Queensland Centre for Medical Genomics, Institute for Molecular Bioscience, University of Queensland, Brisbane, Queensland, Australia.

Pancreatic cancer is molecularly diverse, with few effective therapies. Increased mutation burden and defective DNA repair are associated with response to immune checkpoint inhibitors in several other cancer types. We interrogated 385 pancreatic cancer genomes to define hypermutation and its causes. Mutational signatures inferring defects in DNA repair were enriched in those with the highest mutation burdens. Mismatch repair deficiency was identified in 1% of tumors harboring different mechanisms of somatic inactivation of MLH1 and MSH2. Defining mutation load in individual pancreatic cancers and the optimal assay for patient selection may inform clinical trial design for immunotherapy in pancreatic cancer.
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http://dx.doi.org/10.1053/j.gastro.2016.09.060DOI Listing
January 2017

Loss of INI1 expression in colorectal carcinoma is associated with high tumor grade, poor survival, BRAFV600E mutation, and mismatch repair deficiency.

Hum Pathol 2016 09 14;55:83-90. Epub 2016 May 14.

Cancer Diagnosis and Pathology Research Group, Kolling Institute of Medical Research, St Leonards, NSW, Australia 2065; Department of Anatomical Pathology, Royal North Shore Hospital, St Leonards NSW, Australia 2065; Sydney Medical School, University of Sydney, NSW, Australia 2006. Electronic address:

SMARCB1 is a tumor suppressor gene that encodes for the protein INI1. SMARCB1 is commonly inactivated and INI1 correspondingly shows loss of expression in a range of malignant neoplasms including rhabdoid tumors, renal medullary carcinomas, and epithelioid sarcomas. Loss of INI1 expression has recently been reported in occasional gastrointestinal adenocarcinomas. We sought to investigate the incidence and clinicopathological significance of INI1 loss in colorectal adenocarcinoma (CRC). Immunohistochemistry for INI1 was performed in tissue microarray (TMA) format on a well-characterized and unselected cohort of CRCs undergoing surgical resection. If staining was negative or equivocal in the TMA sections, immunohistochemistry was repeated on whole sections. Focal or widespread negative staining for INI1 was identified in whole sections from 14 (0.46%) of 3051 CRCs. In 7 (50%) of 14 negative cases, the loss of staining was focal, whereas the remainder were characterized by negative staining in all neoplastic cells in whole sections. In the cases with focal staining, loss of staining was frequently found in areas of poor differentiation. Global or focal INI1 loss was strongly associated with higher histological grade, larger tumor size and poor overall survival (P<.001). We conclude that INI1 loss occurs rarely (0.46% when screened by TMA) in CRC, where it is associated with higher grade, larger tumor size, poorer survival, mismatch repair deficiency, and BRAFV600E mutation.
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http://dx.doi.org/10.1016/j.humpath.2016.04.018DOI Listing
September 2016

Mutation specific immunohistochemistry is highly specific for the presence of calreticulin mutations in myeloproliferative neoplasms.

Pathology 2016 Jun 22;48(4):319-24. Epub 2016 Apr 22.

Cancer Diagnosis and Pathology Research Group, Kolling Institute of Medical Research, St Leonards, NSW, Australia; Sydney Medical School, University of Sydney, St Leonards, NSW, Australia; Department of Anatomical Pathology, Royal North Shore Hospital, St Leonards, NSW, Australia; Sydney Vital Translational Research Centre, Royal North Shore Hospital, St Leonards, NSW, Australia. Electronic address:

The identification of somatic calreticulin (CALR) mutations can be used to confirm the diagnosis of a myeloproliferative disorder in Philadelphia chromosome-negative, JAK2 and MPL wild type patients with thrombocytosis. All pathogenic CALR mutations result in an identical C-terminal protein and therefore may be identifiable by immunohistochemistry. We sought to test the sensitivity and specificity of mutation specific immunohistochemistry for pathogenic CALR mutations using a commercially available mouse monoclonal antibody (clone CAL2). Immunohistochemistry for mutant calreticulin was performed on the most recent bone marrow trephine from a cohort of patients enriched for CALR mutations and compared to mutation testing performed by polymerase chain reaction (PCR) amplification followed by fragment length analysis. Twenty-nine patients underwent both immunohistochemistry and molecular testing. Eleven patients had CALR mutation, and immunohistochemistry was positive in nine (82%). One discrepant case appeared to represent genuine false negative immunohistochemistry. The other may be attributable to a 12 year delay between the bone marrow trephine and the specimen which underwent molecular testing, particularly because a liver biopsy performed at the same time as molecular testing demonstrated positive staining in megakaryocytes in extramedullary haematopoiesis. All 18 cases which lacked CALR mutation demonstrated negative staining. In this population enriched for CALR mutations, the specificity was 100%; sensitivity 82-91%, positive predictive value 100% and negative predictive value 90-95%. We conclude that mutation specific immunohistochemistry is highly specific for the presence of CALR mutations. Whilst it may not identify all mutations, it may be very valuable in routine clinical care.
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http://dx.doi.org/10.1016/j.pathol.2016.03.002DOI Listing
June 2016

Loss of expression of BAP1 is very rare in non-small cell lung carcinoma.

Pathology 2016 Jun 21;48(4):336-40. Epub 2016 Apr 21.

Sydney Medical School, University of Sydney, St Leonards, NSW, Australia; Cancer Diagnosis and Pathology Research Group, Kolling Institute of Medical Research, St Leonards, NSW, Australia; Department of Anatomical Pathology, Royal North Shore Hospital, St Leonards, NSW, Australia; Sydney Vital Translational Research Centre, Royal North Shore Hospital, St Leonards, NSW, Australia. Electronic address:

Germline mutations of the BAP1 gene have been implicated in a cancer predisposition syndrome which includes mesothelioma, uveal melanoma, cutaneous melanocytic lesions, renal cell carcinoma, and possibly other malignancies. Double hit inactivation of BAP1 with subsequent loss of expression of the BAP1 protein also occurs in approximately 50% of mesotheliomas. The link between BAP1 mutation and lung cancer is yet to be fully explored. We sought to assess BAP1 expression in a large cohort of lung cancers undergoing surgery with curative intent. We searched the Anatomical Pathology database of our institution for lung cancer patients undergoing surgery with curative intent between 2000 and 2010. Immunohistochemistry for BAP1 was then performed in tissue microarray format. Our cohort included 257 lung cancer patients, of which 155 (60%) were adenocarcinomas and 72 (28%) were squamous cell carcinomas, with no other subtype comprising more than 3%. BAP1 loss of expression was found in only one lung cancer. We conclude that BAP1 mutation occurs very infrequently (0.4%) in non-small cell lung cancer. Given that the pathological differential diagnosis between lung carcinoma and mesothelioma may sometimes be difficult, this finding increases the specificity of loss of expression for BAP1 for the diagnosis of mesothelioma.
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http://dx.doi.org/10.1016/j.pathol.2016.03.005DOI Listing
June 2016

Loss of BAP1 expression is very rare in peritoneal and gynecologic serous adenocarcinomas and can be useful in the differential diagnosis with abdominal mesothelioma.

Hum Pathol 2016 May 29;51:9-15. Epub 2015 Dec 29.

Sydney Medical School, University of Sydney, NSW Australia 2006; Cancer Diagnosis and Pathology Research Group, Kolling Institute of Medical Research, St Leonards, NSW Australia 2065; Department of Anatomical Pathology, Royal North Shore Hospital, St Leonards, NSW Australia 2065; Sydney Vital Translational Research Centre, Royal North Shore Hospital, Pacific Highway St Leonards, NSW 2065. Electronic address:

Gynecologic and primary peritoneal serous carcinoma may be difficult to distinguish from abdominal mesotheliomas clinically, morphologically, and immunohistochemically. BAP1 double-hit inactivation and subsequent loss of protein expression have been reported in more than half of all abdominal mesotheliomas. We therefore sought to investigate the expression of BAP1 in serous carcinoma and explore its potential utility as a marker in the differential diagnosis with mesothelioma. We searched the computerized database of the Department of Anatomical Pathology, Royal North Shore Hospital, Australia, for all cases of gynecologic and peritoneal serous carcinomas and mesotheliomas diagnosed between 1998 and 2014. Immunohistochemistry for BAP1 was then performed on tissue microarray sections. Cases with completely absent nuclear staining in the presence of a positive internal control in nonneoplastic cells were considered negative. If staining was equivocal (eg, absent nuclear staining but no internal control), staining was repeated on whole sections. Loss of BAP1 expression was found in only 1 of 395 (0.3%) serous carcinomas but in 6 of 9 (67%) abdominal mesotheliomas (P < .001) and 131 of 277 (47%) thoracic mesotheliomas (P < .001). We conclude that BAP1 loss occurs extremely infrequently in gynecologic and peritoneal serous adenocarcinomas, whereas it is very common in mesotheliomas including abdominal mesothelioma. Therefore, although positive staining for BAP1 cannot be used to exclude a diagnosis of mesothelioma, loss of BAP1 expression can be used to very strongly support a pathological diagnosis of abdominal mesothelioma over serous carcinoma.
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http://dx.doi.org/10.1016/j.humpath.2015.12.012DOI Listing
May 2016

Genomic analyses identify molecular subtypes of pancreatic cancer.

Nature 2016 Mar 24;531(7592):47-52. Epub 2016 Feb 24.

Queensland Centre for Medical Genomics, Institute for Molecular Bioscience, The University of Queensland, St Lucia, Brisbane, Queensland 4072, Australia.

Integrated genomic analysis of 456 pancreatic ductal adenocarcinomas identified 32 recurrently mutated genes that aggregate into 10 pathways: KRAS, TGF-β, WNT, NOTCH, ROBO/SLIT signalling, G1/S transition, SWI-SNF, chromatin modification, DNA repair and RNA processing. Expression analysis defined 4 subtypes: (1) squamous; (2) pancreatic progenitor; (3) immunogenic; and (4) aberrantly differentiated endocrine exocrine (ADEX) that correlate with histopathological characteristics. Squamous tumours are enriched for TP53 and KDM6A mutations, upregulation of the TP63∆N transcriptional network, hypermethylation of pancreatic endodermal cell-fate determining genes and have a poor prognosis. Pancreatic progenitor tumours preferentially express genes involved in early pancreatic development (FOXA2/3, PDX1 and MNX1). ADEX tumours displayed upregulation of genes that regulate networks involved in KRAS activation, exocrine (NR5A2 and RBPJL), and endocrine differentiation (NEUROD1 and NKX2-2). Immunogenic tumours contained upregulated immune networks including pathways involved in acquired immune suppression. These data infer differences in the molecular evolution of pancreatic cancer subtypes and identify opportunities for therapeutic development.
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http://dx.doi.org/10.1038/nature16965DOI Listing
March 2016

NRASQ61R Mutation-specific Immunohistochemistry is Highly Specific for Either NRASQ61R or KRASQ61R Mutation in Colorectal Carcinoma.

Appl Immunohistochem Mol Morphol 2017 08;25(7):475-480

*Sydney Medical School, University of Sydney, Sydney †Cancer Diagnosis and Pathology Research Group, Kolling Institute of Medical Research ‡Sydney Vital Translational Research Centre §Department of Anatomical Pathology, Royal North Shore Hospital, St Leonards ∥Histopath Pathology, North Ryde, NSW, Australia ¶Auckland UniServices Sequenom Facility, Liggins Institute #IGENZ Ltd., Auckland, New Zealand.

Anti-epidermal growth factor receptor-targeted therapy is only indicated in RAS wild-type colorectal carcinomas (CRCs). It is recommended that both NRAS and KRAS mutation testing to be performed before a CRC is considered RAS wild-type. Given that mutation-specific immunohistochemistry (IHC) has been shown to be sensitive and specific for the detection of NRAS mutations in melanoma, we assessed the specificity of NRAS mutation-specific IHC in CRC. IHC was performed on tissue microarrays containing 2823 consecutive CRC undergoing surgery with curative intent using a novel mutation-specific antibody to the protein produced by the NRAS mutation (clone SP174). Tissue microarrays were assessed by 2 observers and all IHC-positive or equivocal cases were repeated on whole sections to confirm the result. Positive cases then underwent molecular testing by matrix-assisted laser desorption/ionization-time of flight polymerase chain reaction. In total, 22 of 2823 (0.8%) CRCs demonstrated confirmed positive staining with complete interobserver concordance. RAS mutations were confirmed in all IHC-positive CRCs. In total, 11 cases harbored the NRASQ61R mutation. Surprisingly, 11 cases demonstrated the KRASQ61R mutation. We conclude that mutation-specific IHC with this currently available NRASQ61R antibody is highly specific for the presence of either NRASQ61R or KRASQ61R mutations in CRC. We caution that we did not assess the sensitivity of IHC and that this antibody does not detect other RAS mutations. Therefore, negative staining does not exclude a clinically significant RAS mutation. However, positive staining confirms the presence of an NRASQ61R or KRASQ61R mutation without the need for further molecular testing.
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http://dx.doi.org/10.1097/PAI.0000000000000333DOI Listing
August 2017

Mismatch repair deficiency as a prognostic factor in mucinous colorectal cancer.

Mod Pathol 2016 Mar 15;29(3):266-74. Epub 2016 Jan 15.

Cancer Diagnosis and Pathology Research Group, Kolling Institute of Medical Research, St Leonards, NSW, Australia.

There is some uncertainty about pathological grading of mucinous colorectal adenocarcinoma, defined as colorectal cancer demonstrating at least 50% mucinous differentiation. Under the WHO 2000 classification mucinous colorectal cancer was considered high grade. However under the current WHO 2010 classification microsatellite unstable/mismatch repair-deficient (MSI/MMRd) mucinous colorectal cancer is considered low grade, whereas microsatellite stable/mismatch repair proficient (MSS/MMRp) tumours are high grade. However there is little empirical evidence for this approach. We therefore compared the long term survival of patients with MSI/MMRd vs MSS/MMRp mucinous colorectal cancer in a large unselected cohort of patients undergoing surgery at our institution from 1998 to 2011. There were 2608 patients in the cohort, of which 264 (10.1%) were mucinous. 95 (36%) of the mucinous tumours were microsatellite unstable. The all-cause 5-year survival of mucinous MSI/MMRd colorectal cancer was similar to that of non-mucinous low-grade colorectal cancer (73 vs 67%, P=0.368), and significantly better than that of both non-mucinous high-grade (73 vs 53%, P<0.001) and mucinous MSS/MMRp colorectal cancer (73 vs 57%, P=0.023). The 5-year survival of mucinous MSS/MMRp colorectal cancer was slightly better than that of non-mucinous high-grade patients (57 vs 53%, P=0.027), but significantly worse than that of non-mucinous low-grade colorectal cancer (57 vs 67%, P=0.018). In multivariate Cox regression analysis, conventional histological grade based on glandular differentiation maintained prognostic significance (P=0.003) whereas MSI/MMRd status just failed to be statistically significant (P=0.062). Our findings support the WHO 2010 approach that as a group mucinous MSS/MMRp colorectal cancers are biologically aggressive. However, grading based exclusively on MSI/MMR status may be overly simplistic as conventional grading based on the degree of glandular differentiation still holds greater prognostic significance in multivariate analysis.
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http://dx.doi.org/10.1038/modpathol.2015.159DOI Listing
March 2016

Loss of BAP1 Expression Occurs Frequently in Intrahepatic Cholangiocarcinoma.

Medicine (Baltimore) 2016 Jan;95(2):e2491

From the Cancer Diagnosis and Pathology Research Group, Kolling Institute of Medical Research, St Leonards, NSW, Australia (JA, LS, AC, MT, NW, MF, CWT, AJG); Institute of Pathology, University Hospital Heidelberg, Heidelberg, Germany (BG, MR, AS, WW, PS); Department of Anatomical Pathology, Royal North Shore Hospital, St Leonards (LS, AC, MF, AJG); Histopath Pathology, North Ryde (CWT); Sydney Medical School, University of Sydney, Sydney (JA,CWT, RCS, AM, JSS, TJH, AJG); Upper Gastrointestinal Surgical Unit, Royal North Shore Hospital, North Shore Private Hospital, St Leonards; Discipline of Surgery, University of Sydney (AM, JSS, TJH); Macquarie University Hospital, Macquarie University, Sydney (JSS); Department of Anatomical Pathology, SYDPATH, St Vincents Hospitals, Darlinghurst, NSW, Australia (AC); Department of Pathology and Diagnostics, ARC-NET Research Center (RTL, NS, AS); Department of Surgery, University and Hospital Trust of Verona, Verona, Italy (AR); and Sydney Vital Translational Research Centre, Royal North Shore Hospital, Pacific Highway, St Leonards, NSW, Australia (AJG).

BRCA1-associated protein 1 (BAP1) is a deubiquitinating enzyme that functions as a tumor suppressor gene. Double hit BAP1 inactivation has been reported in a range of tumor types, including intrahepatic cholangiocarcinoma (ICC), sometimes in association with germline mutation.We performed immunohistochemistry for BAP1 on a well-characterized cohort of 211 ICC patients undergoing surgical resection with curative intent at 3 institutions based in 3 different countries. The median age at diagnosis was 65 years (range, 36.5-86) and 108 (51%) were men. Negative staining for BAP1 (defined as completely absent nuclear staining in the presence of positive internal controls in nonneoplastic cells) occurred in 55 ICCs (26%). BAP1 loss predicted a strong trend toward improved median survival of 40.80 months (95% CI, 28.14-53.46) versus 24.87 months (95% CI, 18.73-31.01), P = 0.059). In a multivariate model including age, sex, BAP1 status, tumor stage, tumor grade, lymphovascular invasion, and tumor size, female sex was associated with improved survival (hazard ratio [HR] 0.54; 95% CI, 0.34-0.85), while advanced tumor stage and lymphovascular invasion (HR 1.89; 95% CI, 1.09-3.28) correlated with decreased survival. In a multivariate analysis, high grade tumors were associated with BAP1 loss (odds ratio [OR] 3.32; 95% CI, 1.29-8.55), while lymphatic invasion was inversely associated with BAP1 loss (OR 0.36; 95% CI, 0.13-0.99).In conclusion, we observed a trend toward improved prognosis in ICC associated with absent expression of BAP1 and an association of BAP1 loss with higher histological grade and absent lymphatic invasion. Female sex was associated with improved survival while advanced tumor stage and lymphatic invasion were associated with decreased survival.
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http://dx.doi.org/10.1097/MD.0000000000002491DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4718285PMC
January 2016

Fumarate Hydratase-deficient Uterine Leiomyomas Occur in Both the Syndromic and Sporadic Settings.

Am J Surg Pathol 2016 May;40(5):599-607

*University of Sydney ¶¶Cancer Genetics, Hormones and Cancer Group, Kolling Institute of Medical Research, Royal North Shore Hospital, Sydney †Cancer Diagnosis and Pathology Research Group, Kolling Institute of Medical Research §Department of Anatomical Pathology ¶Familial Cancer Clinic, Royal North Shore Hospital, St Leonards ‡Douglass Hanly Moir Pathology ∥Histopath Pathology, North Ryde #Department of Medical Oncology, Hereditary Cancer Clinic, Prince of Wales Hospital, Randwick **Department of Medical Oncology, Concord Hospital, Concord West ††Department of Tissue Pathology and Diagnostic Oncology, Royal Prince Alfred Hospital, Camperdown, NSW ‡‡Department of Anatomical Pathology, Mater Hospital, South Brisbane, Qld, Australia §§Šikl's Department of Pathology, University Hospital, Faculty of Medicine in Pilsen, Charles University in Prague, Prague, Czech Republic ∥∥Department of Pathology and Laboratory Medicine, Calgary Laboratory Services, University of Calgary, Calgary, AB, Canada.

Hereditary leiomyomatosis and renal cell carcinoma (HLRCC) syndrome secondary to germline fumarate hydratase (FH) mutation presents with cutaneous and uterine leiomyomas, and a distinctive aggressive renal carcinoma. Identification of HLRCC patients presenting first with uterine leiomyomas may allow early intervention for renal carcinoma. We reviewed the morphology and immunohistochemical (IHC) findings in patients with uterine leiomyomas and confirmed or presumed HLRCC. IHC was also performed on a tissue microarray of unselected uterine leiomyomas and leiomyosarcomas. FH-deficient leiomyomas underwent Sanger and massively parallel sequencing on formalin-fixed paraffin-embedded tissue. All 5 patients with HLRCC had at least 1 FH-deficient leiomyoma: defined as completely negative FH staining with positive internal controls. One percent (12/1152) of unselected uterine leiomyomas but 0 of 88 leiomyosarcomas were FH deficient. FH-deficient leiomyoma patients were younger (42.7 vs. 48.8 y, P=0.024) and commonly demonstrated a distinctive hemangiopericytomatous vasculature. Other features reported to be associated with FH-deficient leiomyomas (hypercellularity, nuclear atypia, inclusion-like nucleoli, stromal edema) were inconstantly present. Somatic FH mutations were identified in 6 of 10 informative unselected FH-deficient leiomyomas. None of these mutations were found in the germline. We conclude that, while the great majority of patients with HLRCC will have FH-deficient leiomyomas, 1% of all uterine leiomyomas are FH deficient usually due to somatic inactivation. Although IHC screening for FH may have a role in confirming patients at high risk for hereditary disease before genetic testing, prospective identification of FH-deficient leiomyomas is of limited clinical benefit in screening unselected patients because of the relatively high incidence of somatic mutations.
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http://dx.doi.org/10.1097/PAS.0000000000000573DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4830748PMC
May 2016

Loss of expression of BAP1 is a useful adjunct, which strongly supports the diagnosis of mesothelioma in effusion cytology.

Mod Pathol 2015 Oct 31;28(10):1360-8. Epub 2015 Jul 31.

Cancer Diagnosis and Pathology Research Group, Kolling Institute of Medical Research, Sydney, NSW, Australia.

Although most mesotheliomas present with pleural effusions, it is controversial whether mesothelioma can be diagnosed with confidence in effusion cytology. Therefore, an ancillary marker of malignant mesothelial cells applicable in effusions would be clinically valuable. BRCA-1-associated protein (BAP1) is a tumor suppressor gene, which shows biallelic inactivation in approximately half of all mesotheliomas. We investigated whether loss of BAP1 expression by immunohistochemistry can be used to support a diagnosis of mesothelioma in effusion cytology. Immunohistochemistry for BAP1 was performed on cell blocks and interpreted blinded. 43 of 75 (57%) effusions associated with confirmed mesothelioma showed negative staining with positive internal controls. Of 57 effusions considered to have atypical mesothelial cells in the absence of a definitive diagnosis of mesothelioma, 8 cases demonstrated negative staining for BAP1. On follow-up six of these patients received a definitive diagnosis of mesothelioma in the subsequent 14 months (two were lost to follow-up immediately, and mesothelioma could not be excluded). Only 5 of 100 consecutive benign effusions were interpreted as BAP1 negative. One of these patients died soon after and mesothelioma could not be excluded. On unblinded review the four other patients with apparently negative BAP1 staining but no malignancy lacked convincing positive staining in non-neoplastic cells suggesting that BAP1 immunohistochemistry may have initially been misinterpreted. 47 effusions with adenocarcinoma were BAP1 positive. We conclude that loss of BAP1 expression, while not definitive, can be used to support the diagnosis of mesothelioma in effusion cytology. We caution that interpretation of BAP1 immunohistochemistry on cell block may be difficult and that convincing positive staining in non-neoplastic cells is required before atypical cells are considered negative. We also note that BAP1 loss is not a sensitive test as it occurs in only half of all mesotheliomas and cannot be used to exclude the diagnosis.
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http://dx.doi.org/10.1038/modpathol.2015.87DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4761613PMC
October 2015

A patient-derived subrenal capsule xenograft model can predict response to adjuvant therapy for cancers in the head of the pancreas.

Pancreatology 2015 Jul-Aug;15(4):397-404. Epub 2015 May 10.

Cancer Surgery Group, Kolling Institute of Medical Research, The University of Sydney, Royal North Shore Hospital, St Leonards, New South Wales, 2065, Australia. Electronic address:

Background: Although gemcitabine is commonly used as adjuvant therapy for pancreatic adenocarcinoma and pancreaticobiliary-type periampullary cancers, not all patients appear to benefit. This translational study evaluates the potential of a patient-derived subrenal capsule pancreatic cancer xenograft (SRCPCX) model to identify within eight weeks after surgery those tumours which will respond to gemcitabine.

Methods: SRCPCXs from 32 pancreatectomy patients were established in six to ten NOD/SCID mice per patient. After four weeks the mice were randomly assigned to receive gemcitabine or saline for four more weeks. After eight weeks, gemcitabine response in the grafts was evaluated by the percentage of tumour growth inhibition (%TGI), histological morphology and immunohistochemical markers (Ki-67, CK7 and cleaved caspase-3). These were collated into an Overall Response. Survival was assessed by Kaplan-Meier and Cox multivariate analyses.

Results: 375 of 450 pieces of tissue from 27 of 31 patients were evaluable. In 90% of patients, histopathological and immunostaining features of saline-treated control grafts were concordant with their original tumours. At follow up, six of 15 patients whose tumours had an Overall Response to gemcitabine died, compared with ten of 12 whose tumours did not respond (P = 0.025, Fisher's exact test). This was associated with improved survival on Kaplan-Meier analysis (P = 0.013). Cox multivariate analysis indicated that Overall Response, stage and grade were independent predictors of survival.

Conclusion: This SRCPCX model retains major histopathological and immunohistochemical characteristics of the original tumour and when a combination of measures is used, enables early assessment of tumour sensitivity to gemcitabine in pancreatic cancers.
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http://dx.doi.org/10.1016/j.pan.2015.04.008DOI Listing
April 2016

Loss of expression of BAP1 predicts longer survival in mesothelioma.

Pathology 2015 Jun;47(4):302-7

1Cancer Diagnosis and Pathology Research Group, Kolling Institute of Medical Research, St Leonards 2Department of Anatomical Pathology, Royal North Shore Hospital, St Leonards 3Histopath Pathology, North Ryde 4Sydney Medical School, University of Sydney, Sydney 5Sydney Vital Translational Research Centre, Royal North Shore Hospital, Pacific Highway, St Leonards, NSW, Australia.

BRCA1-associated protein 1 (BAP1) is a tumour suppressor gene frequently inactivated in mesothelioma, rarely also in association with germline mutation. BAP1 mutations have been associated with improved prognosis and distinct clinicopathological features. We sought to determine the clinicopathological significance of BAP1 immunohistochemistry (IHC) in mesothelioma.We performed IHC on a tissue microarray (TMA) cohort comprising all available thoracic mesotheliomas encountered during the period 1991-2014 at our institution (n = 229). All cases were independently reviewed to confirm the diagnosis and subclassify as epithelioid, sarcomatoid or biphasic. The median age at diagnosis was 72 years; 188 (82.1%) were male; 120 (52.4%) were epithelioid (median survival 13.0 months), 67 (29.3%) sarcomatoid (median survival 5.6 months) and 42 (18.3%) biphasic (median survival 10.6 months). Negative staining for BAP1 (defined as completely absent nuclear staining in the presence of positive internal controls in non-neoplastic cells) occurred in 106 (46.3%) mesotheliomas. There was complete interobserver concordance for BAP1 IHC status. BAP1 loss was strongly associated with younger age at onset (p < 0.01) and epithelioid differentiation (p < 0.01). BAP1 loss predicted an improved median survival of 16.11 months (95% CI 12.16-20.06) versus 6.34 months (95% CI 5.34-7.34), p < 0.01. In a multivariate model including age, gender and histological type, BAP1 loss, younger age and epithelioid differentiation remained protective (all p < 0.01).If our results are confirmed by others, BAP1 IHC may have a role to predict prolonged survival or triage formal genetic testing for germline BAP1 mutation in patients presenting with mesothelioma.
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http://dx.doi.org/10.1097/PAT.0000000000000250DOI Listing
June 2015

Whole genomes redefine the mutational landscape of pancreatic cancer.

Nature 2015 Feb;518(7540):495-501

Queensland Centre for Medical Genomics, Institute for Molecular Bioscience, The University of Queensland, St Lucia, Brisbane, Queensland 4072, Australia.

Pancreatic cancer remains one of the most lethal of malignancies and a major health burden. We performed whole-genome sequencing and copy number variation (CNV) analysis of 100 pancreatic ductal adenocarcinomas (PDACs). Chromosomal rearrangements leading to gene disruption were prevalent, affecting genes known to be important in pancreatic cancer (TP53, SMAD4, CDKN2A, ARID1A and ROBO2) and new candidate drivers of pancreatic carcinogenesis (KDM6A and PREX2). Patterns of structural variation (variation in chromosomal structure) classified PDACs into 4 subtypes with potential clinical utility: the subtypes were termed stable, locally rearranged, scattered and unstable. A significant proportion harboured focal amplifications, many of which contained druggable oncogenes (ERBB2, MET, FGFR1, CDK6, PIK3R3 and PIK3CA), but at low individual patient prevalence. Genomic instability co-segregated with inactivation of DNA maintenance genes (BRCA1, BRCA2 or PALB2) and a mutational signature of DNA damage repair deficiency. Of 8 patients who received platinum therapy, 4 of 5 individuals with these measures of defective DNA maintenance responded.
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http://dx.doi.org/10.1038/nature14169DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4523082PMC
February 2015

Medullary colorectal carcinoma revisited: a clinical and pathological study of 102 cases.

Ann Surg Oncol 2015 Sep 9;22(9):2988-96. Epub 2015 Jan 9.

Sydney Medical School, University of Sydney, Sydney, NSW, Australia.

Aim: Medullary carcinoma is a recently described subtype of mismatch repair deficient (MMRd) colorectal carcinoma (CRC) which, despite being poorly differentiated by traditional morphological criteria, has been reported to have a good prognosis. We investigated the pathological and clinical features of medullary CRC in an unselected cohort of CRCs undergoing surgical resection.

Methods: All CRCs resected within a single health district database from 1998 to 2012 were categorized prospectively and underwent retrospective review to identify 91 medullary CRCs, with 11 additional cases from 2013 to 2014. Strict criteria were employed to diagnose medullary carcinoma requiring both MMRd and greater than 90 % of the tumor to demonstrate typical morphology, including solid growth. The demographic and pathological features, as well as all-cause survival, were compared with other CRCs, and specifically to other MMRd CRCs.

Results: From 1998 to 2012, 91 of 3,295 CRCs (2.8 %) were of the medullary type. Medullary CRC was more likely to arise in females than males (3.3:1; p < 0.0001), the elderly (mean age 77 vs. 71 years; p < 0.001), and the right colon (86 %; p < 0.0001). All medullary CRCs demonstrated MMR deficiency (considered an inclusion criteria) and 86 % were BRAFV600E-mutated (p < 0.0001). Thirty-day mortality after resection was higher in medullary CRC (4.6 vs. 1.7 %; p = 0.049). On univariate analysis, survival was not better than well-differentiated or other MMRd tumors. However, using a multivariate model, a medullary phenotype was protective (hazard ratio of death 0.54, 95 % CI 0.30-0.96; p = 0.037).

Conclusions: Medullary CRC is more common than previously reported, frequently presents with locally advanced disease, and may be associated with higher mortality at 30 days after resection. Despite this, when strict criteria are used for diagnosis, the overall survival is favorable when compared with CRCs with equivalent demographic and pathological characteristics.
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http://dx.doi.org/10.1245/s10434-014-4355-5DOI Listing
September 2015

A detailed clinicopathologic study of ALK-translocated papillary thyroid carcinoma.

Am J Surg Pathol 2015 May;39(5):652-9

*Cancer Diagnosis and Pathology Research Group §§Sydney Vital Translational Research Centre, Kolling Institute of Medical Research §University of Sydney Endocrine Surgical Unit **Hormones and Cancer Group, Cancer Genetics Laboratory, Kolling Institute of Medical Research Departments of ¶Anatomical Pathology #Endocrinology, Royal North Shore Hospital, St Leonards †Department of Anatomical Pathology SYDPATH, St Vincent's Hospital ‡Kinghorn Cancer Centre and Cancer Research Program, Garvan Institute of Medical Research, Darlinghurst ∥Histopath Pathology, North Ryde ††Department of Tissue Pathology and Diagnostic Oncology, Royal Prince Alfred Hospital, Camperdown ‡‡University of Sydney, Sydney, NSW, Australia.

Pathogenic ALK translocations have been reported in papillary thyroid carcinoma (PTC). We developed and validated a screening algorithm based on immunohistochemistry (IHC), followed by fluorescence in situ hybridization (FISH) in IHC-positive cases to identify ALK-rearranged PTC. IHC and FISH were performed in a cohort of 259 thyroid carcinomas enriched for aggressive variants. IHC was positive in 8 cases, 6 confirmed translocated by FISH (specificity 75%). All 251 IHC-negative cases were FISH negative (sensitivity 100%). Having validated this approach, we performed screening IHC, followed by FISH in IHC-positive cases in an expanded cohort. ALK translocations were identified in 11 of 498 (2.2%) of all consecutive unselected PTCs and 3 of 23 (13%) patients with diffuse sclerosing variant PTCs. No ALK translocations were identified in 36 PTCs with distant metastases, 28 poorly differentiated (insular) carcinomas, and 20 anaplastic carcinomas. All 14 patients with ALK translocations were female (P=0.0425), and translocations occurred at a younger age (mean 38 vs. 48 y, P=0.0289 in unselected patients). ALK translocation was an early clonal event present in all neoplastic cells and mutually exclusive with BRAF mutation. ALK translocation was not associated with aggressive clinicopathologic features (size, stage, metastasis, vascular invasion, extrathyroidal extension, multifocality, risk for recurrence, radioiodine resistance). We conclude that 2.2% of PTCs are ALK-translocated and can be identified by screening IHC followed by FISH. ALK translocations may be more common in young females and diffuse sclerosing variant PTC but do not connote more aggressive disease.
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http://dx.doi.org/10.1097/PAS.0000000000000368DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4415964PMC
May 2015

EGFR mutation specific immunohistochemistry is a useful adjunct which helps to identify false negative mutation testing in lung cancer.

Pathology 2014 Oct;46(6):501-8

1Cancer Diagnosis and Pathology Group, Northern Translational Cancer Research Unit, Kolling Institute of Medical Research, St Leonards 2Department of Anatomical Pathology, Royal North Shore Hospital, St Leonards 3Sydney Medical School, University of Sydney, Sydney 4HistoPath Pathology, North Ryde 5Tissue Oncology and Diagnostic Oncology, Royal Prince Alfred Hospital, Camperdown 6School of Medicine, University of Western Sydney, Sydney 7Department of Medical Oncology, Royal North Shore Hospital, St Leonards 8Kinghorn Cancer Centre and Cancer Research Program, Garvan Institute of Medical Research, Darlinghurst 9University of NSW, Sydney 10Department of Anatomical Pathology, SydPath, St Vincent's Hospital, Darlinghurst, NSW, Australia.

Mutations in EGFR guide treatment in non-small cell lung cancer (NSCLC). The most common mutations, exon 19 (delE746-A750) and exon 21 (L858R), can be identified by mutation specific immunohistochemistry (IHC). We present our prospective experience of universal reflex IHC and molecular testing in non-squamous NSCLC in the routine clinical setting.A total of 411 specimens from 332 patients were encountered over two years. Of these, 326 (98%) patients underwent EGFR IHC, 15 (5%) were positive for exon 19 deletions and 27 (8%) for exon 21 (L858R); 244 (73%) patients underwent molecular testing. Seventy-six mutations in 64 patients (19% of all patients encountered; 26% with sufficient material for testing) were identified. These comprised nine exon 18 (G719X) mutations, three also with exon 20 mutations; 24 exon 19 deletions, six also with exon 20 mutations; 23 exon 21 (L858R), three also with exon 20 mutations; and 8 exon 20 alone.All 15 exon 19 IHC positive patients were proven mutated (100% specificity, 63% sensitivity). Twenty-two of 27 exon 21 IHC positive cases were proven mutated while three patients had insufficient material for molecular testing (92% specificity, 96% sensitivity). The overall specificity and sensitivity of IHC for any EGFR mutation was 95% and 58%. Five patients initially thought to be wild type for EGFR but IHC positive underwent repeat molecular testing because of the discrepancy which confirmed the IHC result in three cases (60%).We conclude IHC is very specific but not sensitive. Whilst IHC cannot replace molecular testing, it is a useful adjunct which requires minimal tissue and identifies false negative molecular results which occurred in 5% of our patients with eventually confirmed EGFR mutations.
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http://dx.doi.org/10.1097/PAT.0000000000000141DOI Listing
October 2014

A further investigation of combined mismatch repair and BRAFV600E mutation specific immunohistochemistry as a predictor of overall survival in colorectal carcinoma.

PLoS One 2014 25;9(8):e106105. Epub 2014 Aug 25.

Sydney Medical School, University of Sydney, Sydney, NSW, Australia; Cancer Diagnosis and Pathology Research Group, Kolling Institute of Medical Research, St Leonards, NSW, Australia; Sydney Vital Translational Research Centre, Royal North Shore Hospital, Pacific Highway, St Leonards, NSW, Australia; Department of Anatomical Pathology, Royal North Shore Hospital, St Leonards, NSW, Australia.

Mutation specific immunohistochemistry (IHC) is a promising new technique to detect the presence of the BRAFV600E mutation in colorectal carcinoma (CRC). When performed in conjunction with mismatch repair (MMR) IHC, BRAFV600E IHC can help to further triage genetic testing for Lynch Syndrome. In a cohort of 1426 patients undergoing surgery from 2004 to 2009 we recently demonstrated that the combination of MMR and BRAFV600E IHC holds promise as a prognostic marker in CRC, particularly because of its ability to identify the poor prognosis MMR proficient (MMRp) BRAFV600E mutant subgroup. We attempted to validate combined MMR and BRAFV600E IHC as a prognostic indicator in a separate cohort comprising consecutive CRC patients undergoing surgery from 1998 to 2003. IHC was performed on a tissue microarray containing tissue from 1109 patients with CRC. The 5 year survivals stratified by staining patterns were: MMRd/BRAFwt 64%, MMRd/BRAFV600E 64%, MMRp/BRAFwt 60% and MMRp/BRAFV600E 53%. Using the poor prognosis MMRp/BRAFV600E phenotype as baseline, univariate Cox regression modelling demonstrated the following hazard ratios for death: MMRd/BRAFwt HR = 0.71 (95%CI = 0.40-1.27), p = 0.31; MMRd/BRAFV600E HR = 0.74 (95%CI = 0.51-1.07), p = 0.11 and MMRp/BRAFwt HR = 0.79 (95%CI = 0.60-1.04), p = 0.09. Although the findings did not reach statistical significance, this study supports the potential role of combined MMR and BRAF IHC as prognostic markers in CRC.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0106105PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4143358PMC
December 2015
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