Primary Squamous Cell Carcinoma of the Breast: A Case Report

Background Primary squamous cell carcinoma of the breast is a metaplastic carcinoma subtype and a rare tumor accounting for 0.1% of all breast cancers. Its clinical behavior should not be correlated with the standard infiltrating duct carcinoma of breast as it follows an atypical presentation in terms of tumor size, lymph node and systemic spread. Proper treatment for this rare kind of breast cancer is still unclear. We report the clinical and evolutionary aspects of a new case of primary epidermoid carcinoma of the breast. Case Presentation A 42-year-old woman, without significant medical history, has been followed since 2018 for bilateral lumps of the breasts, the largest lump was at the right lower outer quadrant and measured 2,5 × 2 cm. Ultrasound aspect suggested a fibrocystic breast disease, classified ACR3. No biopsy was made at that time. This lump was gradually progressive in size, so the patient had underwent an excision of the breast tumor in July 2021. The histological study found a 2.5 cm well-differentiated keratinizing squamous cell carcinoma of the breast grade III according to Scarff-Bloom–Richardson score (SBR). Immunohistological study was negative for both hormone receptors and human epidermal growth factor receptor 2 (HER2). The average ki-67 labeling index was 50%. An extensive workup ruled out other primary sites or metastatic disease. Then, the patient had underwent the modified radical mastectomy of Patey on 07/21.Microscopic examination of the tumors revealed a high-grade ductal carcinoma in situ with comedonecrosis. No abnormality was found in the axillary lymph nodes. The patient was referred to the oncology department for adjuvant therapy. She was provided with adjuvant chemotherapy regimen consisting of three courses of Epirubicin at the dose of 100 mg/m 2 and Cyclophosphamide at the dose of 500 mg/m 2 , then she received three courses of Docetaxel 75 mg/m 2 and Carboplatin AUC 5. Adjuvant radiotherapy was delivered. Our patient will have a clinical examination every four to six months for the first five years, then annually. Four to six months after the end of the radiotherapy treatment, then every year, we are planning a mammography and an ultrasound examination. The patient tolerated the treatment and first controls did not suggest any recurrence of the disease. Conclusion Squamous cell carcinomas of the breast are rare, they have no clinical or radiological specificity. The treatment is based on surgery, radiotherapy and chemotherapy. The prognosis remains controversial. Studies on larger series are necessary to determine if primary pure squamous cell carcinoma of the breast should be treated as a separate entity or as a common type of breast cancer.