Aggressive squamous cell carcinoma in a patient on the Janus kinase inhibitor ruxolitinib

Ruxolitinib, an orally administered inhibitor of Janus kinase (JAK) 1 and 2, which are intracellular nonreceptor tyrosine kinases, is used to treat patients with myelofibrosis1 and is found to have significant clinical benefits including reductions in splenomegaly and total symptom score.2 Ruxolitinib is also found to be superior to standard single-agent therapy in controlling hematocrit, reducing the spleen volume, and improving symptoms associated with polycythemia vera.3 The most common adverse events associated with ruxolitinib is anemia and thrombocytopenia, which rarely lead to drug discontinuation.2 Of note, 5-year efficacy data on ruxolitinib showed 17.1% of patients on ruxolitinib went on to have basal cell carcinomas (BCCs) or squamous cell carcinomas (SCCs) compared with only 2.7% of patients on best-available therapy.4 Current ruxolitinib prescriber information labels warn of the risk of nonmelanoma skin cancers, and performing periodic skin examinations is recommended.5 Skin cancers occurring in patients treated with ruxolitinib have been reported in the dermatology literature to display more aggressive biological behavior and metastatic potential.6, 7 We present another case of a patient having aggressive cutaneous malignancy after ruxolitinib initiation and urge physicians to be aware of this associated risk.