A 57-year-old woman presented with a 2-year history of a palpable mass in the upper inner quadrant of the right breast. A 1.1-cm, poorly circumscribed, firm tumor nodule was noted, consisting of 2 histologically distinct lesions in the same location, with some areas showing purely well-differentiated invasive ductal carcinoma and others composed of granular cell tumor. In 1 area, the 2 tumors collided and infiltrated each other. The invasive ductal carcinoma was admixed with ductal carcinoma in situ of solid and cribriform types. To our knowledge, this is the first case report demonstrating colocalization of these 2 neoplasms, which raises questions regarding causal relationship. We also review the literature on granular cell tumor of the breast.