[Primary epidermoid carcinoma of the breast mimicking an abscess]

Squamous cell carcinoma of the breast is a basal-like phenotype metaplastic cancer with poor prognosis. It is often diagnosed at earlier stages based on voluminous palpable mass not detected on screening. Squamous cell carcinoma should be suspected in patients with abscess, as is the case with our 44-year old female patient presenting with a mass in the left breast diagnosed as a cyst with abscess formation measuring 5,4cm x 5cm on mammography combined with ultrasound (A). Surgical biopsy was performed. Anatomopathological examination showed tumor proliferation with large carcinomatous lobules and clear squamous differentiation greater than 90% (B). Tumor cells were very atypical and showed many mitotic figures. Immunohistochemical study showed tumor cells expressing cytokeratins 5/6 (C). Proliferation index was 85% (D). Hormone receptors and hercept test were negative. The diagnosis of metaplastic squamous cell carcinoma was retained. Our patient underwent left mastectomy with axillary dissection and adjuvant chemotherapy followed by radiotherapy. The patient didn't developed locoregional recurrence or distant metastasis during a 9-month follow-up period.