Primary intracystic squamous cell carcinoma of the breast: A case report and review of the literature

Primary intracystic squamous cell carcinoma (SCC) of the breast is an extremely rare entity and has a low incidence in comparison with other breast cancers. We report a rare case of primary intracystic SCC in a 45-year-old woman who presented with a cystic lump in the right breast. Cytological smears of the fluid aspirated from the breast tumor revealed malignant squamous cells dispersed in single and occasional groups along with numerous cyst macrophages, suggesting cystic SCC. Histological study of the mastectomy specimen confirmed the diagnosis of primary intracystic SCC. Although the presence of abundant foamy macrophages in the background of fine needle aspiration cytology smears of the breast suggest benign breast lesion, when associated with malignant squamous cells, these suggest cystic primary SCC or metastatic SCC. The primary SCC should not be confused with metaplastic change in other breast carcinomas.