A Case of Pure Squamous Cell Carcinoma of the Breast in an Elderly Woman Diagnosed by Cytology

: A n 85-year-old woman presented with a mass in the left breast. A3 7mm lobulated mass including enhancement of a cyst of 37mm was detected by sonography. An axillary lymph node had increased to 16 mm. Atypical cells dyed by light green and orange G were identified by fine needle aspiration and cytology. She was diagnosed with left breast cancer(cT2N1M0, Stage II B), histologically suspected to be squamous cell carcinoma. She underwent a left-breast-conserving surgery and axillary lymph node dissection. On pathology, a cyst of 34×30mm was noted. The tumor grew from inside the cyst to the surround- ing tissue and it had a trend for keratinocytes. Lymph node metastases affected 1/11. By immunostaining, the tumor was found to be ER(+), PgR(-), HER2(-), CK5/6(+), p40(+), mammaglobin(-), and GCDFP15(-). There was no component of ductal carcinoma. She received radiotherapy to the left breast and tamoxifen as an adjuvant therapy. Squamous cell carcinoma of the breast is rare. We encountered a case of pure squamous cell carcinoma of the breast in an elderly woman. We report this case with a discussion of the relevant literature.