[A case report of matrix-producing carcinoma of the breast].

A 43 -year-old woman with a palpable mass in the right breast consulted a neighborhood doctor. She was diagnosed with right breast cancer after core needle biopsy, and she was referred to our hospital. Mammography revealed an indistinct mass with calcification in the lower outer quadrant of the right breast. Ultrasonography revealed a hypoechoic mass with a high echo spot. Magnetic resonance imaging (MRI) revealed a high intensity tumor with peripheral enhancement. The patient underwent mastectomy with sentinel lymph node(SN) biopsy and axillary lymph node dissection. Histologically, the tumor was composed of a solid-tubular carcinoma with a centrally located metaplastic cartilaginous element. There was an abrupt transition between these components, without intervening spindle cells or osteoclastic cells. Subtyping via immunohistochemical analysis for estrogen receptor (ER), progesterone receptor (PgR), and human epidermal growth factor receptor 2 (HER2) demonstrated that the tumor was triple negative (TN). The histological diagnosis was matrix-producing carcinoma (MPC). Adjuvant chemotherapy was administered, and she has been recurrence-free. MPC has unique features, such as emphasis of the peripheral zone of the tumor by using contrast enhanced-computed tomography (CT) and gadolinium-diethylene triamine pentaacetic acid (Gd-DTPA) MRI. Most cases of MPC that have been reported were TN. The 5 year survival rate for MPC is poorer than that for breast cancer. In Japan, 7 cases of MPC recurrence have been reported within 2.5 years, suggesting that careful follow-up is necessary for 2-3 years after surgery.