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 ofspiradenocylindroma, which, in addition to areas of conventionalgrowth, manifested an adenomatous component. This consisted ofcompactly situated, well-developed glands having small roundlumens lined by inner pale to eosinophilic cells and surrounded byan outer well-formed peripheral layer of myoepithelial cells, whichreacted 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 butsignificant portion of the tumors, but in 2 cases it was extensive,comprising approximately 20% of the tumor area. In 1 of these2 cases, the luminal epithelium showed atypia including rare, atypicalmitotic figures. In addition, there were foci of glands showingmyoepithelial cell loss. As this alteration was limited and fairly wellcircumscribed within the tumor bulk, we regard it as an ‘‘atypicaladenomatous component,’’ but we cannot exclude the possibility thatthis may represent an incipient apocrine carcinoma, despiteuneventful follow-up. Three cases also manifested clear cell areas.Immunohistochemical studies demonstrated that myoepithelial proliferationand overgrowth accounted for the clear cell change in someof the lesions.