Malignant clear cell hidradenoma of the lip.

An interesting variety of cutaneous tumors of the head and neck, tumors of the eccrine differentiation, are seldom recognized. The most recent reports of these tumors appear in the dermatologic literature, probably due to the majority of them being located in the trunk and the extremities. Malignant varieties of these tumors do exist and must be treated as aggressively as more common tumors of the head and neck region. Tumors with eccrine differentiation are among a large variety of cutaneous tumors that present in the head and neck. These tumors are far less common than basal cell and squamous cell carcinomas of the head and neck. Malignant clear cell hidradenomas, a variant of the more common benign clear cell hidradenoma, is one such type of tumor of the eccrine differentiation. This is a rare tumor seldom reported in sites of the head and neck. A case of a 47-year-old white male with such a tumor of the lower half of his lip is presented. This report is particularly concerned with the histopathology of the tumor, its unique etiology, and the applicability of the lip switch flap (Stein-Abbe-Estlander) in the reconstruction of the surgical defect following total tumor excision.