Objectives: Solid second primary cancers (SPC) have become an issue of extensive research. The purpose of the present study was to estimate the standardised incidence ratio (SIR) and the absolute excess risk (AER) of SPC in patients with splenic marginal zone lymphoma (SMZL).Methods: We investigated the incidence of additional cancers in 129 patients consecutively diagnosed with SMZL in three Italian haematological centres, asking the cooperating doctors for additional information on initial and subsequent therapies and on the onset and type of second cancers. Results: Twelve SPC were recorded (9.3%); the 3- and 5-yr cumulative incidence rates were 5.5% and 18.3% respectively, with an SIR of 2.03 [95% confidence interval (CI): 1.05-3.56; P < 0.05; AER = 145.81]. Of 12 SPC observed, four were urinary tract neoplasms (SIR, 3.70; 95% CI: 1.01-9.48; P < 0.05; AER = 70.06), four were lung cancers (SIR, 9.16; 95% CI: 1.41-13.25; P < 0.05; AER = 85.50) and the other four were hepatic carcinoma, endometrial cancer, breast cancer and colorectal cancer.Conclusions: Our findings evidence a high frequency of additional cancers in patients with SMZL and suggest that the incidence rate of SPC is significantly different from that expected in the general population. The frequency of cases with urinary tract and lung malignancies in our series is higher than expected. Although confirmatory data are needed, it is our opinion that SMZL patients are at risk of second cancer and should be carefully investigated on diagnosis and monitored during the follow-up.