Malignant Sweat Gland Tumors.

Malignant sweat gland neoplasms are a confusing area within dermatopathology, with many entities reported under several designations in the literature. This review describes the key clinical and histopathologic features of select malignant adnexal neoplasms, including porocarcinoma, papillary carcinoma, adenoid cystic carcinoma, cribriform carcinoma, apocrine hidradenocarcinoma, malignant mixed tumor of the skin, syringoid carcinoma, cylindrocarcinoma, spiradenocarcinoma, mucinous carcinoma, polymorphous sweat gland carcinoma, microcystic adnexal carcinoma, secretory carcinoma of the skin, and primary cutaneous signet ring cell carcinoma. For entities with overlapping features, differential diagnoses are discussed.