Primary Squamous Cell Carcinoma of Breast: A Short Report and Immunohistochemical Review

Primary squamous cell carcinoma (SCC) of the breast is classified by the World Health Organization as a metaplastic carcinoma, meaning that it is made up solely of squamous cells that have undergone metaplasia and frequently show variable degrees of keratinization. Less than 0.1% of all invasive breast carcinomas are primary SCCs, making them incredibly uncommon. The exact cause and development of SCC in the breast remain uncertain. Some suggest it could represent an extreme form of squamous cell metaplasia progressing into adenocarcinoma, potentially explaining its mixed forms. Existing literature reveals only a handful of documented cases to date. This malignancy is notably aggressive, typically lacking hormone receptor expression (triple negative), resistant to standard treatments, and associated with a bad prognosis.