Breast plasmacytomas are extremely rare entities that can be seen as primary malignant neoplasms in the absence of bone involvement or as secondary neoplasms from disseminated multiple myeloma. Clinicians should be aware of this entity, as it may mimic benign and malignant lesions in the breast. Microscopically, immature plasmacytomas may mimic other neoplasms, so caution should be made on histological examination to ensure the correct diagnosis and corresponding therapy. Here we present a case of a plasmablastic plasmacytoma of the breast in a 55-year-old woman that was originally thought to be an angiosarcoma.