Eccrine Porocarcinoma Presenting as a Hand Cyst.

Eccrine porocarcinoma is a rare tumor that arises from the epithelium of the eccrine ducts, with a tendency for metastatic spread and a high rate of local recurrence after excision. It was first described in 1963 by Pinkus and Mehregan and can present clinically as a nodule, erosive plaque or a polypoid growth that may ulcerate. The variable clinical appearance of these lesions can make diagnosis challenging and could delay appropriate treatment. If metastasis occurs the prognosis is poor, with a reported mortality rate of up to 80%. We report an uncommon presentation of porocarcinoma as a cyst on the dorsum of the right hand in a 37-year-old man. Only 8% of porocarcinomas occur in the upper extremity and only 3% are on the hand. Furthermore, the tumor is more common in females and mean age at diagnosis is 67 years. Treatment is with wide local excision with free tumor borders confirmed by biopsy, which has been shown to be curative in 70% to 80% of patients.