Primary mucinous carcinoma of the skin.

Only twenty-seven cases of primary mucinous carcinoma of the skin have been reported. Three additional cases are included in this paper. The clinical presentation is distinctive; they are found most commonly in middle-aged, black males in the head and neck region as painless nodules, usually less than 3 cm in diameter. Previous reports have indicated the probable sweat gland origin of these tumours; one of our cases demonstrates a transition from a solid hidradenoma-like pattern to nests of tumour cells floating in mucin lakes, adding support for the sweat gland hypothesis. The clinical behaviour is relatively benign; late recurrences are common but metastases are rare. Only one case had widespread metastases. Although the histological appearance is distinctive, other primary sites first must be excluded. Local excision is the treatment of choice.