Mucinous differentiation in adnexal sweat gland tumors.

We report an eccrine acrospiroma, on the cheek of a 29-year-old female, in which the presence of abundant mucinous (goblet cell) metaplasia closely mimicked a primary mucoepidermoid carcinoma. To determine the frequency of mucinous differentiation in benign adnexal sweat gland tumors, we evaluated sixty-five cases in hematoxylin and eosin stained sections for the presence of goblet cells and sixty of these for mucicarmine positivity. Goblet cell metaplasia was seen in 3 of 12 acrospiromas, 1 of 8 mixed tumors, and in 1 of 9 cases of syringocystadenoma papilliferum. All goblet cells were positive for mucicarmine, except in one case of acrospiroma, where goblet cells were not detected on the section stained with mucicarmine. In addition, intracellular mucin, inclusive of goblet cells, was seen in 5 of 12 acrospiromas, 1 of 11 poromas, 5 of 8 mixed tumors, 3 of 13 spiradenomas, 1 of 5 cylindromas, 3 of 9 cases of syringocystadenoma papilliferum and 1 of 3 nipple adenomas. The majority of the tumors had both extracellular mucicarmine positivity (40 of 60) and luminal mucicarmine positivity (39 of 60). We conclude that mucinous differentiation in sweat gland tumors, as defined by the presence of goblet cells and/or intracellular mucicarmine positivity, is common and does not indicate aggressive behavior. Mucinous differentiation in benign sweat gland tumors should not be confused with more aggressive mucoepidermoid carcinomas of salivary gland origin or adenosquamous carcinoma.