Synchronous presentation of breast carcinoma with plasmacytoid cytomorphology and multiple myeloma

Plasmacytoid morphology is often encountered in both lobular and ductal carcinomas of the breast. The presentation of breast carcinoma in patients with a known history of lymphoma or multiple myeloma has been described in the literature. However, to the best of our knowledge, the synchronous presentation of breast carcinoma and multiple myeloma has not been reported. Here we report the first case of the simultaneous occurrence of breast carcinoma with plasmacytoid morphology and multiple myeloma in a 74-year-old patient, which presented challenges in making the diagnosis on fine-needle aspiration biopsy (FNAB) of the breast.