A case of matrix-producing carcinoma of the breast treated with preoperative chemotherapy

BACKGROUND: Matrix-producing carcinoma (MPC) is a rare tumor accounting for 0.1% of all breast cancers. Although MPC is usually triple-negative breast cancer, there have been few reports of preoperative chemotherapy for MPC that is considered chemotherapy-resistant. Herein, we report a case of MPC that was successfully treated with preoperative chemotherapy. CASE DESCRIPTION: The patient was a 47-year-old woman diagnosed with right multiple breast cancer, clinical stage IIA. One of the tumors was identified as MPC and the other was invasive ductal carcinoma. The maximum tumor diameter of MPC was 3.8-cm. On immunohistochemistry, the tumor cells of MPC tested negative for estrogen receptor (ER), progesterone receptor (PgR), and human epidermal growth factor receptor 2 (HER2). The Ki67 index was 90%. Preoperative chemotherapy was performed. EC (epirubicin 90 mg/m(2) and cyclophosphamide 600 mg/m(2)) was administered every 3 weeks for a total of 4 courses, followed by 12 courses of weekly paclitaxel (80 mg/m(2)). Then, she underwent right skin-sparing mastectomy, sentinel lymph node biopsy, and deep inferior epigastric perforator flap reconstruction. There was no metastasis to the sentinel lymph nodes. Postoperative pathological results showed that the residual tumor of the MPC measured only 0.1 cm. On the other hand, the residual tumor of the invasive ductal carcinoma was 0.7 cm. Endocrine therapy with oral tamoxifen was initiated for the invasive ductal carcinoma. Three years after surgery, no recurrence was observed. It has been reported that prognosis was correlated with residual cancer after preoperative chemotherapy. In addition, preoperative chemotherapy is of high clinical significance for the selection of postoperative treatment. CONCLUSIONS: Although our case of MPC was successfully treated with preoperative chemotherapy, the standard of care for MPC remains uncertain. Development of a new targeted therapy for MPC is warranted.