Matrix-Producing Carcinoma of the Breast Achieves Pathological Complete Response with Pembrolizumab-Containing Neoadjuvant Chemotherapy

Abstract

A 53-year-old woman presented with a 2.5-cm lump in the lower inner quadrant of the right breast. It was diagnosed as a matrix-producing carcinoma of the breast (MPC) of triple-negative subtype (TNBC) via core needle biopsy. Neoadjuvant chemotherapy with paclitaxel, carboplatin, and pembrolizumab followed by epirubicin, cyclophosphamide, and pembrolizumab was performed, resulting in clinical complete response. Partial resection of the right breast and sentinel lymph node biopsy were performed, and pathological examination showed pathological complete response. MPC is generally resistant to anthracycline/taxane-based chemotherapy for breast cancer, and there are no data for the efficacy of the pembrolizumab-containing regimen for MPC. Based on the present case, neoadjuvant chemotherapy with a pembrolizumab-containing regimen may be appropriate for MPC of TNBC.