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

Abstract

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.

Keywords: adenocarcinoma; extramammary paget’s disease; neoadjuvant radiation treatment; perianal disease.

Figure 1. Ulcerated appearance of Paget’s disease overlying a significant surface area at the time of referral to radiation oncology A) affecting the vulva and the perineum, B) affecting the perianal region and right buttock

Figure 2. Infiltration of squamous epithelium with single atypical cells with frequent mitotic figures and PAS-positive intracytoplasmic vacuoles

The atypical cells were positive for CK7, CK20, CDX2, EMA, and CEA on immunohistochemistry. These findings are diagnostic of Paget’s disease, most likely from a rectal adenocarcinoma PAS: periodic acid-Schiff

Figure 3. Varying degrees of increased FDG activity around the perianal region, natal cleft, and anterior perineum (white arrows) on PET imaging

A) sagittal plane. B) axial plane PET: positron emission tomography

Figure 4. Dosimetric plan showing the various doses within the pelvis in Gy, with the corresponding colour legend located on the top-left hand corner

CT planning scan in A) axial plane, B) coronal plane, and C) sagittal plane CT: computed tomography