Collagenous spherulosis in an adenomyoepithelioma of the breast

Abstract

Collagenous spherulosis (CS) is an incidental finding that usually occurs in association with benign proliferative and preinvasive lesions. Adenomyoepithelioma is a biphasic neoplasm of the breast, composed of both luminal epithelial and myoepithelial cells. Despite the common epimyoepithelial histogenesis, CS has never been described in association with adenomyoepithelioma. This report describes the case of a 48 year old woman who presented with CS of the breast in an adenomyoepithelioma. The combination of these two benign lesions led to diagnostic difficulties; namely, differentiation from adenoid cystic carcinoma, but also cribriform carcinoma and cylindroma of the breast. Antibodies to the oestrogen receptor, progesterone receptor, p63, and c-kit (CD117) proved to be useful adjuncts to differentiate between these lesions.

Figure 1

Adenomyoepithelioma with collagenous spherulosis. (A) Low power view disclosing the well circumscribed and non-encapsulated nature of the lesion. (B) Areas showing typical histological features of lobulated adenomyoepithelioma. (C, D) Details of the nests, which were composed of luminal and myoepithelial cells, arranged around focal aggregates of well circumscribed, deeply eosinophilic acellular spherules. These nests imperceptibly merged with the typical adenomyoepitheliomatous areas (C, arrow). (E) Detail of the peripheral areas disclosing luminal epithelial and myoepithelial cells arranged around the collagen IV positive acellular spherules.

Figure 2

Immunohistochemical findings. (A) Oestrogen receptor. (B) Progesterone receptor. (C) p63 expression in the areas of collagenous spherulosis. Inset: note that the cells lining the collagen spherules are strongly positive for p63. (D) Lack of c-kit (CD117) expression in the collagenous spherulosis in contrast to the strong positivity in adjacent normal luminal cells (arrow).