[Treatment Regimens for Breast Cancer in Elderly Patients in Whom the Diagnosis Was Switched from Malignant Phyllodes Tumor to Spindle-Cell Carcinoma after Surgery].

The patient was a 79-year-old woman with a left breast mass. Magnetic resonance imaging showed a cystic mass with a diameter of 10×8 cm and an ulcer in the upper outer quadrant and the nipple-areola region of the left breast. Intracystic carcinoma was thus suspected. A mass with a diameter of 1 cm was found in the upper outer quadrant of the right breast. Needle biopsy revealed that a cystic mass in the left breast was diagnosed as a malignant phyllodes tumor. A mass in the right breast was diagnosed as Luminal A breast cancer. The clinical tumor stage was T1N0M0. Computed tomography showed no enlarged bilateral axillary lymph nodes. In the left breast, mastectomy was performed with extensive skin excision above the tumor. In the right breast, partial mastectomy was performed with sentinel lymph node biopsy. On postoperative pathological examination, the diagnosis of left breast tumor was triple-negative spindle-cell carcinoma. The pathological tumor stage was diagnosed as T4bNxM0. Taking into consideration treatment according to breast cancer stage and age, we selected 4 courses of weekly-paclitaxel, endocrine therapy, irradiation to the left chest wall, and irradiation to the residual right breast. The preoperative diagnosis was malignant phyllodes tumor. The postoperative diagnosis was switched from malignant phyllodes tumor to spindle-cell carcinoma. It was therefore difficult to determine the presence or absence of additional resection and postoperative treatment regimens. Even though the preoperative diagnosis was a malignant phyllodes tumor, surgical procedures such as sentinel lymph-node biopsy should be considered, taking into account the possibility of breast cancer.