Eccrine syringofibroadenoma with co-existent squamous cell carcinoma.

Eccrine syringofibroadenoma (ESFA) is a rare, benign adnexal tumor arising most often on the extremities of elderly individuals. It is typically a slow-growing, flesh- to reddish-colored nodule or plaque. Histologically, the tumor consists of anastomosing cords of cuboidal epithelial cells surrounded by a fibrovascular stroma containing plasma cells. The cords contain scattered ductal structures lined with cuboidal cells resembling eccrine ducts. The co-existence of ESFA with squamous cell carcinoma has been described, eliciting the term eccrine syringofibroadenoma. The differential diagnosis includes poroma, porocarcinoma, fibroepithelioma of Pinkus and clear cell acanthoma. ESFA stain positively with epithelial membrane antigen and carcinoembryonic antigen. Cytokeratin studies have been inconsistent.