[A Case of Metaplastic Breast Cancer Treated with Neoadjuvant Chemotherapy Combined with Pembrolizumab]

Metaplastic breast carcinoma, a rare subtype(<1% of breast cancers), is typically triple-negative with a poor prognosis. The KEYNOTE-522 trial established pembrolizumab plus chemotherapy as a standard treatment for early-stage, high-risk triple-negative breast cancer. We report a case of metaplastic carcinoma with squamous differentiation achieving pathological complete response after neoadjuvant pembrolizumab-based chemoimmunotherapy. This case suggests that pembrolizumab-based chemoimmunotherapy may be a promising option for chemoresistant metaplastic carcinoma.