A Case of Squamous Cell Carcinoma of the Breast Occurring in Benign Phyllodes Tumor.

A 49-year-old woman visited our hospital after noticing an enlarged left breast mass. After a biopsy, she was diagnosed with fibroadenoma and underwent tumor resection. Postoperative pathology revealed squamous cell carcinoma (SCC) within a benign phyllodes tumor. Following additional resection, adjuvant chemotherapy was administered in accordance with the treatment for triple-negative breast cancer, and the patient has since progressed without recurrence for four years. The occurrence of SCC within a phyllodes tumor is extremely rare, and we report this case through a review of the literature.