Primary ectopic Merkel cell carcinoma without skin involvement—report of a case with prolonged survival

Merkel cell carcinoma is a rare neuroendocrine malignancy that arises from the dermis, in cases of immunocompromised, middle-aged patients or on skin exposed to sunlight. It only rarely presents in extra-cutaneous locations. We present the case of a 63-year-old female with a mass in the adipose tissue of the upper arm, without skin involvement and concurrent axillary lymph node enlargement. She was treated with wide excision and lymph node dissection; pathology led to the diagnosis of Merkel cell carcinoma, and she was subsequently submitted to adjuvant radiotherapy. No signs of recurrence are present 8 years postoperatively. Primary Merkel cell carcinoma can rarely be located in the adipose tissue without skin involvement. In cases of high suspicion, preoperative MRI scan can show the extent of the lesion, as well as lymph metastases.