Melanoma and rituximab: an incidental association?

Rituximab is an anti-CD20 monoclonal antibody increasingly used in haematology and rheumatology, but also in internal medicine and dermatology. It has a good tolerance profile without known increased risk of cancer. We report a case of nodular melanoma with a 4.8 mm Breslow thickness that appeared after 2 years of rituximab in a 45-year-old patient with non-Hodgkin lymphoma. Fifteen additional rituximab-associated melanoma cases in 13 patients have been identified in the literature and in the EudraVigilance database. These patients were treated for various indications and had melanomas, often aggressive, initially diagnosed at a metastatic stage in 31% of cases. Our work raises the question of rituximab accountability in melanoma onset in these immunosuppressed patients. A dermatological monitoring seems necessary in patients treated with rituximab, especially in case of risk factors for melanoma. In case of individual melanoma history, the benefit/risk ratio of initiating rituximab therapy should be carefully assessed.