eP562 - A Case of Perianal Paget's Disease

Purpose/Background: Perianal Paget’s disease is a rare disorder, and the available literature on the subject remains mostly observational. It can arise as a primary tumor or secondary to underlying pelvic visceral malignancy and is often initially misdiagnosed as an inflammatory perianal rash until proper pathologic diagnosis has been confirmed.Methods/Interventions: We present the case of a 76-year-old woman who presented with perianal rash initially treated with topical therapy for two years before a punch biopsy confirmed extramammary Paget’s disease. Physical exam revealed an erythematous macular lesion with portions of ulceration over the left perianal skin and buttock. The patient’s preoperative workup included computed tomography (CT) of the chest, abdomen and pelvis, positron emission tomography (PET) scan, pelvic magnetic resonance imaging (MRI), genetic testing, colonoscopy, cystoscopy, and Pap smear with no evidence of underlying malignancy. She underwent surgical excision of the perianal lesion with 1 cm margins and concomitant temporary diverting colostomy, with plastic surgery providing a temporary closure.Results/Outcomes: Pathology was consistent with Paget’s disease and unfortunately exhibited positive margins medially along the anal verge. She was brought back for re-excision 3 weeks later, and a further 1 cm margin was taken from the medial, perianal aspect where the positive margin was previously noted on pathology. Within the anal canal, less than 1 cm of epithelial tissue was noted, and some rectal mucosa had to be resected to obtain adequate margins. Pathology resulted with focally positive microscopic margins in 3 areas.  After review with medical oncology, radiation oncology, pathology and the patient, the decision was made to proceed with closure with plastic surgery and adjuvant radiation therapy due to the focal microscopic positive margin being amendable to radiation therapy and the high risk of defecatory dysfunction with any additional resection.Conclusion/

Discussion: In conclusion, perianal Paget’s disease is an uncommon and difficult to treat disease due to the high risk of positive margin at resection and 30% risk for recurrence even with negative margins. This case highlights the importance of early recognition of this disease and a multidisciplinary approach to its treatment.Intraoperative view of perianal Paget's lesion