[A case of spindle cell carcinoma of the breast including metaplastic lesion with poor prognosis].

A 57-year-old woman complained of a huge and rapid growing mass with bleeding in the left breast. Breast imaging (CT and MRI)showed a large, irregular and unevenly enhanced tumor with lymph node swelling in the left axilla. Mastectomy and axillary lymph node dissection were performed for control of bleeding from the tumor in the left breast. Pathological diagnosis was spindle cell carcinoma of the breast with transition from papillotubular carcinoma. Although the patient was treated with adjuvant chemotherapy and trastuzumab according to the treatment guideline for conventional breast cancer, she had an early relapse with mediastinal metastasis and died 9 months after operation. The tumor showed metaplastic change from epithelial tumor to spindle cell carcinoma. Because the epithelial part expressed weakly positive estrogen receptor(ER), progesterone receptor(PgR)-negative and HER2-positive, we used trastuzumab for adjuvant therapy. However, part of the spindle cell tumor mainly showed triple-negative, and ER, PgR and HER2 expression were negative, which might explain her poor prognosis for resistance to trastuzumab.