Recurrent squamous cell carcinoma of the breast with undifferentiated features: report of a case.

Squamous cell carcinoma of the breast is a rare type of cancer, the origin of which is still uncertain. We report a case of squamous cell carcinoma of the breast with a recurrent tumor that showed undifferentiated features. The patient was a 55-year-old woman who originally presented with a left breast mass in the upper outer quadrant. Echography showed a 46 x 29 x 23-mm mass with cavity formation, and aspiration cytology confirmed a diagnosis of squamous cell carcinoma. A modified radical mastectomy with level III lymph node dissection was performed. Pathologically, the tumor was composed of squamous cell carcinoma and noninvasive ductal carcinoma. A recurrent tumor showing undifferentiated features was detected in the left forechest 3 months after the operation, and tumorectomy with partial resection of the major and minor pectoralis muscles was performed. Despite intensive therapy including chemotherapy (CEF: cyclophosphamide, epirubicin, 5-fluorouracil) and irradiation (50 Gy), the patient died from pulmonary and skin metastases 20 months after her initial operation. The squamous cell carcinoma of the breast in this patient grew rapidly and her prognosis was poor. Immunohistochemical findings indicated the possibility that the squamous cell carcinoma developed from noninvasive ductal carcinoma of the comedo type, and that the undifferentiated cells from the site of recurrence developed from dedifferentiation of the squamous cell carcinoma.