Malignant hidradenoma--a case report demonstrating insidious histological and clinical progression.

A histologically benign hidradenoma, occurring in a 15-year-old female inadequately excised at first procedure, recurred locally over the course of 11 years and exhibited first local and subsequently regional metastatic spread. The insidious progression was associated with increasing cytological atypia and alteration of epithelial antigenic expression. In view of the rarity of malignant sweat-gland tumours and consequent lack of a specific treatment protocol, this case serves to emphasize the importance of adequate primary local excision, with histological confirmation of clearance, in the management of sweat-gland tumours.