Abstract Breast cancers occurring in women with germline BRCA1 mutations tend to fall into the category of triple-negative or basal-like phenotypes, such as metaplastic carcinoma. Low-grade adenosquamous carcinoma of the breast is a rare variant of metaplastic carcinoma. We present the case of a 49-year-old woman with a past medical history of invasive ductal breast carcinoma 13 years ago, and who was recently diagnosed as having a low-grade adenosquamous carcinoma in the same breast. Genetic analysis of blood DNA revealed a BRCA1 mutation. To our knowledge, BRCA1 mutation in association with a low-grade adenosquamous carcinoma of the breast has not yet been reported. Thus, it may be important to consider the possibility of an association, but supplemental studies are needed.