Invasive Squamous Cell Carcinoma of the Nipple: Case Report With Literature Review.

In this unusual case, a 73-year-old woman presented with bloody discharge from her right breast and skin thickening was observed on subsequent imaging. Clinically, the findings raised concern for Paget disease. A skin punch biopsy was performed, revealing a high-grade infiltrating carcinoma with squamous features. Metaplastic carcinoma was a differential diagnosis, given that this patient had a history of invasive ductal carcinoma and radiation treatment in the same breast. A subsequent central lumpectomy confirmed the diagnosis of invasive squamous cell carcinoma of the nipple, occurring in the context of Bowen disease as a precursor lesion. Notably, there was no evidence of ductal carcinoma in situ in the background breast tissue or conventional invasive ductal carcinoma component. Both in situ and invasive forms of squamous cell carcinomas have been rarely reported in the nipple. This case highlights the importance of considering such a rare diagnosis, especially in patients with a history of breast cancer.