Melanoma and non‐melanoma skin cancers in hairy cell leukaemia: a Surveillance, Epidemiology and End Results population analysis and the 30‐year experience at Memorial Sloan Kettering Cancer Center

Summary Few studies have examined melanoma and non‐melanoma skin cancer (NMSC) incidence rates after a diagnosis of hairy cell leukaemia (HCL). We assessed 267 HCL patients treated at Memorial Sloan Kettering Cancer Center (MSKCC) and Surveillance, Epidemiology and End Results (SEER) data for melanoma and NMSC incidence rates after HCL. Incidence data from MSKCC patients demonstrated a 10‐year combined melanoma and NMSC skin cancer rate of 11·3%, melanoma 4·4% and NMSC 6·9%. Molecular analysis of skin cancers from MSKCC patients revealed activating RAS mutations in 3/9 patients, including one patient with melanoma. Of 4750 SEER patients with HCL, 55 (1·2%) had a subsequent diagnosis of melanoma. Standardized incidence ratios (SIRs) did not show that melanoma was more common in HCL patients versus the general population (SIR 1·3, 95% CI 0·78–2·03). Analysis of SEER HCL patients diagnosed before and after 1990 (approximately before and after purine analogue therapy was introduced) showed no evidence of an increased incidence after 1990. A better understanding of any potential association between HCL and skin cancer is highly relevant given ongoing trials using BRAF inhibitors, such as vemurafenib, for relapsed HCL, as RAS‐mutant skin cancers could be paradoxically activated in these patients.