[A Case of T4b Breast Cancer That Developed 17 Years after Radiofrequency Ablation].

We report a case of T4b breast cancer that developed 17 years after radiofrequency ablation(RFA). The patient was a 64- year-old woman. She had been diagnosed with left breast cancer 17 years ago and had undergone RFA. After radiation therapy, she had been administered AI drugs for 5 years. She was diagnosed with a mass in her left breast and visited our department. At the time of admission, a mass measuring 7 cm in diameter was palpable in her left breast. A needle biopsy revealed the diagnosis of invasive ductal carcinoma. A systemic examination revealed no obvious distant metastasis. A pectoral muscle-sparing mastectomy+partial pectoralis major muscle resection+axillary lymph node dissection+reconstruction using a rhomboid flap was performed. Histopathological findings of the resected specimen showed invasive ductal carcinoma, tumor diameter 53 mm, negative resection margin, and no lymph node metastasis. ER positive, PgR positive, HER2 positive, Ki-67 30%, and the diagnosis was T4bN0M0, Stage ⅢB. After postoperative chemotherapy, radiation therapy was performed. After that, trastuzumab+pertuzumab was administered 17 times. Currently, the patient is being followed up with fulvestrant. Two years after surgery, there has been no obvious metastasis or recurrence.