Spiradenoma and spiradenocylindroma with an adenomatous or atypical adenomatous component: a clinicopathological study of 6 cases.

We report 5 cases of spiradenoma and 1 case of spiradenocylindroma, which, in addition to areas of conventional growth, manifested an adenomatous component. This consisted of compactly situated, well-developed glands having small round lumens lined by inner pale to eosinophilic cells and surrounded by an outer well-formed peripheral layer of myoepithelial cells, which reacted with a variety of myoepithelial cell markers. In 1 case, apocrine secretion was evident in the glandular part of the lesion. In 4 of the 6 cases, the adenomatous component was a minor but significant portion of the tumors, but in 2 cases it was extensive, comprising approximately 20% of the tumor area. In 1 of these 2 cases, the luminal epithelium showed atypia including rare, atypical mitotic figures. In addition, there were foci of glands showing myoepithelial cell loss. As this alteration was limited and fairly well circumscribed within the tumor bulk, we regard it as an "atypical adenomatous component," but we cannot exclude the possibility that this may represent an incipient apocrine carcinoma, despite uneventful follow-up. Three cases also manifested clear cell areas. Immunohistochemical studies demonstrated that myoepithelial proliferation and overgrowth accounted for the clear cell change in some of the lesions.