Deceptive Triple-Negative Breast Cancer of Intermediate Grade: A Case of Rare Microglandular Adenosis-Associated Carcinoma

Breast cancer is the most common cancer among women and the leading cause of cancer-related deaths globally. Ductal carcinoma of no special type is the most prevalent, followed by lobular carcinoma. Finding a triple-negative breast cancer of intermediate grade on core biopsies should raise the possibility of dealing with one of the rare subtypes such as microglandular adenosis (MGA)-associated carcinoma. Here, we present a case of a 40-year-old female, who presented with bilateral breast masses, in which one of them was a high-grade carcinoma and the other turned out to be an MGA-associated carcinoma, which was misdiagnosed initially on the core biopsy as a grade II triple-negative ductal carcinoma of no special type. Such diagnosis is challenging to pathologists, especially on small biopsies where the full morphological spectrum is not evident.