RESUMO
BACKGROUND: Squamous cell carcinoma of the breast is very rare and it is considered to arise from metaplastic change of ductal carcinoma. Metaplastic squamous cell carcinoma (MSC) of the breast includes pure squamous cell carcinoma, metaplastic adenosquamous carcinoma and low grade adenosquamous carcinoma. Most of the cases of MSC of the breast were reported to have lymph node metastasis and this has a worse prognosis than that of conventional invasive ductal carcinoma. METHODS: We collected 17 cases of MSC of the breast from 1,173 cases of breast cancer and analyzed the clinicopathological characteristics. RESULTS: The age range was 31 to 69 years (mean age: 47.2). The mean tumor size was 3.6 cm. Twelve cases (70.6%) had a negative nodal status. The majority of the cases were of a high nuclear grade (grade III: 76.5%), and a high histologic grade (grade III: 88.2%). All the cases had no amplification of HER2, and they were negative for hormonal receptors, except for 2 cases with weak positivity. All the cases showed positivity for EGFR (3+: 14 cases, 1+: 3 cases). Clinical relapse was found in 3 patients on follow up and two of them expired due to lung and bone metastasis. CONCLUSIONS: MSC is associated with high nuclear and histologic grades, a high EGFR expression and they are triple negative for ER, PR, and HER2. The EGFR immunopositivity of MSC suggests a basal-like subtype.