Merkel cell carcinoma associated with tofacitinib therapy

Merkel cell carcinoma (MCC) is a highly aggressive neuroendocrine neoplasm and the second most common cause of skin cancer-related death.1 It is thought to be derived from Merkel cells which reside in the basement layer of the skin and function to provide somatosensory input to the body. A higher incidence of these aggressive malignancies has been seen in patients with B cell neoplasms, solid organ transplants, HIV infections as well as in countries with higher levels of UV radiation.2