Adenomyoepithelioma of the breast: report of two cases with prominent cystic changes and intranuclear inclusions.

Adenomyoepithelioma is a rare breast tumor. Histologically it may disclose different patterns of growth, and some additional features may result in diagnostic errors. We describe 2 cases of adenomyoepithelioma of the breast initially examined by fine-needle aspiration biopsy (FNAB). Cytologic features included hypercellularity, clusters of epithelial and myoepithelial cells with occasional intranuclear inclusions, prominent apocrine metaplasia, and foam cells. Histologically, both tumors were diagnosed as adenomyepithelioma tubular-variant, with prominent myoepithelial clear cells, apocrine metaplasia, and foci of squamous metaplasia. Immunohistochemically, the tumors showed strong positivity for keratins CAM 5.2, AE1/AE3, and EMA in the epithelial component, while the myoepithelial cells reacted with muscle-specific actin (A14 and HHF35) and S-100 protein. We point out that FNAB in this rare tumor may exhibit a varied spectrum of cells that may result in confusion with other lesions, and we call attention to the presence of intranuclear inclusions. The latter observation in the present cases by cytologic and histologic assessment provides and additional feature to the morphological characteristics of adenomyoepithelioma of the breast.