Adenoid Cystic Carcinoma of the Breast.: Value of Immunohistochemical Study in Diagnosis

Abstract

An immunohistochemical study of 5 cases of adenoid cystic carcinoma (ACC) of the breast was performed with antibodies against keratin, EMA, vimentin, S-100 protein, alpha-smooth muscle actin and collagen IV. Results show the following: 1) ACC may be diagnosed and differentiated from ductal carcinoma (invasive or in situ). The key to diagnosis is positivity within tumor masses of alpha-smooth muscle actin, a specific marker for myoepithelial cells. Actin-rich cells are not generally observed in ductal carcinomas, except at the periphery of a few invaded ducts, corresponding to a residual myoepithelial cell layer. Other markers may be positive in both ACC and ductal carcinoma; these are not specific and only the percentage and distribution of positive cells are helpful for diagnosis (small clusters of keratin-positive cells in ACC « versus » most positive cells in ductal carcinoma). 2) The functional pleomorphism of the cell population is underlined with cells differentiating towards epithelium and myoepithelium stained by corresponding markers, and undifferentiated cells unstained by any marker. These results confirm the value of an immunohistochemical study in the diagnosis of ACC of the breast.