Pure apocrine nevus: a report of 4 cases.

Apocrine nevus is a rare tumor composed of increased mature apocrine glands and ductal structures within a fibrous stroma, located predominantly in the reticular dermis. They have been reported in association with apocrine carcinoma, extramammary Paget disease, and syringocystadenoma papilliferum; less commonly a pure apocrine nevus is identified, unassociated with another apocrine proliferation. Clinically apocrine nevi may appear as solitary or multiple nodules or plaques on the scalp, presternal skin, though they are seen most commonly in the axillae. We describe 4 cases of pure apocrine nevus, all of which appeared clinically as painless or mildly tender skin-colored axillary masses, 2 of which were bilateral. In each case, the lesions appeared in adulthood, and patients denied knowledge of congenital or childhood presence. Patients denied pruritis, discharge, bleeding, or antecedent trauma. Grossly, the specimens consisted of subcutaneous, multicystic ill-defined nodules. Biopsy showed prominent apocrine glands composed of irregularly columnar luminal cells with eosinophilic cytoplasm arranged in a somewhat organoid pattern filling the reticular dermis and extending into the subcutaneous adipose tissue. The glandular luminal cells displayed decapitation secretion. There was a paucity of pilosebaceous units. In one case, the overlying epidermis was papillomatous. The deepest portion of one specimen had lactational change simulating a lactational adenoma. No atypia was seen in either the glandular structures or the stroma. The adjacent sebaceous and eccrine structures were normal. The histologic features and immunohistochemical profile in relation to other apocrine lesions will be reviewed.