Extensive Extramammary Paget's Disease With Underlying Perianal Adenocarcinoma: The Role of Neoadjuvant Radiation Treatment.

Extramammary Paget's disease (EMPD) is an uncommon entity, and secondary EMPD is even rarer. To our knowledge, this report involves one of the only three cases in the literature to date regarding the use of neoadjuvant radiation therapy in the treatment of secondary EMPD. A 65-year-old woman's EMPD had become more widespread over the years to involve buttocks, perineum, anus, vulva, and vagina. Given the knowledge of potential secondary EMPD, suspicious perianal lesions were biopsied. Histology and immunohistochemistry staining confirmed adenocarcinoma. Our patient was treated with neoadjuvant radiation therapy, along with concurrent chemotherapy. This was followed by pelvic exenteration, which confirmed a complete response from the neoadjuvant treatment. We discuss her presentation, investigations, and treatment regimen in detail. In addition, we review the treatment of secondary EMPD as reported in previously published literature.