Successful treatment of biphasic metaplastic sarcomatoid carcinoma of the breast by evaluation of immunohistochemical markers.

Biphasic metaplastic sarcomatoid carcinoma (MSC) of the breast is rare and aggressive. Patients with metaplastic breast carcinomas tend to have poor outcomes with a high risk of recurrence following pri- mary surgery. Most reports have shown that systemic therapy appears to be less effective. We report a case of a 42-year-old female who presented with a large (14 cm) cauliflower breast mass. Biopsy revealed a poorly differentiated sarcoma. Initially, neo-adjuvant concurrent chemoradiotherapy with a sarcoma regimen was prescribed, and the tumor regressed to a large ulcer. Subsequent biopsy showed invasive ductal carcinoma (estrogen receptor, progesterone receptor stained weakly, 5%, Her2:2+) and disappearance of the sarcomatous component. Second-line neoadjuvant therapy was designed according to the histologic features of infiltrating ductal carcinoma, which led to nearly a complete response. A modified radical mastectomy of the right breast and axillary dissection was performed followed by monoclonal antibody (trastuzumab) therapy for 6 months due to the surgical specimen showing Her2:3+. The treatment course went smoothly with a good response. The patient had no evidence of disease at 18 months.