Estrogen receptor-positive primary squamous cell carcinoma of the breast

Pure primary squamous cell carcinoma of the breast (SCCB) represents around 0.1% of breast carcinomas. Diagnosis requires independence from adjacent skin without metastatic disease. SCCB is often large at presentation with nonspecific mammographic and ultrasound findings. It is typically hormone receptor negative and aggressive. Mastectomy and adjuvant chemotherapy is the most common treatment, although treatment guidelines are not well established. We present a case of pure primary SCCB detected by high risk screening mammogram and treated with breast conserving surgery, chemotherapy, and radiation. We discuss clinical, radiologic, and pathologic findings.