Am J Dermatopathol 2019 Feb 25. Epub 2019 Feb 25.
Department of Dermatology, Venereology and Allergology, University Medical Centre, Göttingen, Germany.
AL-amyloidoma is considered to be a variant of primary cutaneous marginal zone lymphoma (pcMZL). A 51-year-old white man presented a 2 × 2-cm erythematous to brownish waxy plaque on the back of the scalp. The plaque was first noticed 16 years ago. It was asymptomatic, and the patient was otherwise healthy. The lesion was excised. Histological examination revealed dermal deposits of amyloid and a subtle perivascular infiltrate, predominately consisting of plasma cells. Infiltrating cells expressed CD79a, bcl2, and IgG and were negative for bcl6, CD56, and IgM. A monoclonal light-chain expression of lambda (lambda:kappa = 10:1) was demonstrated by in situ hybridization. The diagnosis of pcMZL, presenting as an AL-amyloidoma, was made because staging procedures excluded systemic manifestation of lymphoma, monoclonal gammopathy, and systemic amyloidosis. Cutaneous amyloid deposits with monoclonal plasma cell proliferation can occur as a result of monoclonal gammopathy/plasmocytoma or as a rare manifestation of pcMZL. Systemic B-cell lymphoma and systemic monoclonal plasma cell proliferations have to be excluded.