Department of Surgery, Okayama Saiseikai General Hospital
Center for Innovative Clinical Medicine, Okayama University Hospital
Department of Diagnostic Pathology, Kurashiki Medical Center
Department of Palliative and Supportive Medicine, Okayama University Hospital
We treated two patients with a rare metaplastic carcinoma of the breast. Patient 1：A 32-year-old woman presented with a rapidly growing mass（ 7cm） in her right breast. We diagnosed cT3N0M0 Stage IIB breast cancer and performed a radical resection. The pathological diagnosis was triple-negative metaplastic carcinoma with a Ki-67 value ＞30%. Postoperative adjuvant chemotherapy and radiotherapy were performed. Patient 2：A 66-year-old postmenopausal woman presented with a left breast mass. We diagnosed cT1N0M0 Stage I breast cancer and performed a radical resection. The pathological diagnosis was triple-negative metaplastic carcinoma with a Ki-67 value ＞30%. Postoperative adjuvant chemotherapy was performed. Patients 1 and 2 have achieved relapse-free survivals of 1 year＋2 months and 10 months, respectively. Metaplastic carcinoma of the breast is a rare tumor, and its prognosis is not favorable. The only available treatment is that used for invasive ductal carcinoma；a more specific treatment has not been established. The accumulation of further similar cases and the development of a novel effective treatment are desired.