Primary Breast Pure Metaplastic Squamous Cell Carcinoma: A Breast Abscess With Squamous Metaplasia and Malignant Transformation That Mimics Condylomata Acuminata.

Pure metaplastic squamous cell carcinomas (MSCC) of the breast are rare. We report the case of a 57-year-old woman who presented with a breast abscess in whom a papillomatous lesion was identified during incision and drainage. The initial biopsy demonstrated hyperplastic squamous epithelium with koilocytic atypia, raising the possibility of condylomata acuminata. Subsequent wide excision revealed extensive squamous metaplasia with invasive squamous cell carcinoma arising within a cystic papillary lesion consistent with pure MSCC of the breast. Immunohistochemistry revealed positivity for p63 and negativity for p16, estrogen receptor, progesterone receptor, and human epidermal growth receptor 2. The investigations excluded human papillomavirus infections, cutaneous origins, and extramammary primary squamous cell carcinomas. Following early local recurrence, the patient underwent mastectomy and axillary dissection. Adjuvant radiotherapy and chemotherapy were also administered. This case highlights the diagnostic challenges and aggressive behavior of pure MSCC and emphasizes the importance of clinicopathological correlations and multidisciplinary management.