Aggressive Merkel Cell Carcinoma After Janus Kinase Inhibitor Ruxolitinib for Polycythemia Vera.

Merkel cell carcinoma (MCC) is a rare neuroendocrine carcinoma of the skin. It is highly aggressive and represents the second most common cause of skin cancer-related death. Ruxolitinib is an orally administered selective inhibitor of Janus associated kinases1 and 2, which is used in the management of patients with symptomatic myelofibrosis and polycythemia vera who are non-responders or intolerant to hydroxyurea. Herein, we report the case of a 47-year-old woman with a 14-year history of chronic myeloproliferative syndrome initially treated with hydroxyurea for 4 years. She was then enrolled in the Response trial and treated for 7 years with ruxolitinib subsequently developing an MCC. This report shows the possibility of development of MCC in patients treated with ruxolitinib. Periodic skin examination is indicated in patients who undergo ruxolitinib therapy, especially if they have a history of skin cancer; dermatologists and oncohematologists should be aware of this possibility in order to introduce appropriate preventive strategies.