Primary Squamous Cell Carcinoma of the Breast: a Case Report and Immunohistochemical Features for Differential Diagnosis

We present a 68-year-old postmenopausal woman with a rapidly growing right breast mass. It was diagnosed as “invasive ductal carcinoma” on tru-cut biopsy owing to infiltrative pattern and c-erbB-2 (HER2/neu) and progesterone receptor positivities. Partial response was obtained after four cure chemotherapy (adriamycin and cyclophosphamide). Then, she underwent a modified radical mastectomy with axillary lymph node dissection (level III). Grossly, a white-tan, solid, ill-defined tumor with 5 cm diameter located in the upper inner and outer quadrant of the breast was detected. Central portion of the tumor showed necrotic and hemorrhagic changes. Microscopic examination revealed poorly differentiated squamous cell carcinoma (SCC) having intraductal epithelial hyperplasia with squamous cell metaplasia and multiple small tumor foci at the periphery. The tumor had patchy necrotic, hemorrhagic and fibrotic areas representing regressive changes due to chemotherapy effect. Immunohistochemically, the tumor stained diffusely with CK7, CK8, CK19, HMW-CK and E-cadherin, whereas focally with CEA. Estrogenand progesterone receptors and c-erbB-2 were negative in the tumor. Five out of 20 lymph nodes dissected from the specimen were metastatic. Clinically, other organs were ruled out as the originating site of the tumor. She had taken oral chemotherapy (capecitabine) after surgery and has been living healthy for one year.