The Birth of an Adenoid Cystic Carcinoma

Abstract

Adenoid cystic carcinoma is a rare malignancy of exocrine glands defined by the presence of a dual population of cells (epithelial and myoepithelial cells) organized in varying combinations of cribriform, tubular, and solid patterns.1,2 This neoplasm most frequently originates in the salivary glands; however, it can also occur in other anatomical sites, including the breast.1,3 More than 90% of adenoid cystic carcinomas of the breast harbor the recurrent translocation t(6;9), resulting in the MYB-NFIB fusion gene, which leads to MYB overexpression.4 Adenoid cystic carcinoma in situ has been described in the breast; however, its identifica-tion is not trivial.3 Here, we illustrate an in situ adenoid cystic carcinoma partially involving a mammary duct in a 68-year-old woman with primary adenoid cystic carci-noma of the right breast. The double population of cells composing this intraductal lesion can be appreciated by its immunohistochemical profile (Figure 1). Given that the neoplastic cells of the in situ lesion already express MYB, our findings are consistent with the notion that MYB overexpression is an early event in the tumorigen-esis of adenoid cystic carcinomas.4,5