E0143 - Hemorrhoid or Cancer: Anorectal Mucosal Melanoma Discovered During Hemorrhoidectomy

Gabrielle Sanford, MD¹, Jeremy Polman, DO, MS, MBA², Marshall Stagg, MD¹, Kelly Finan, MD^3
1LSUHSC Baton Rouge Internal Medicine Residency Program at Our Lady of the Lake, Baton Rouge, LA; ²Baton Rouge General Medical Center, Baton Rouge, LA; ³Our Lady of the Lake Regional Medical Center, Baton Rouge, LA

Introduction: Anorectal mucosal melanoma (ARM) is an exceptionally uncommon and aggressive malignancy that is often found at advanced stages of the disease, primarily due to its non-specific presentation. Primary ARM accounts for less than 2% of all melanomas. Because of its rarity, it is often misdiagnosed as benign conditions such as hemorrhoids or polyps on initial exam, thus leading to a delay in diagnosis and treatment. Additionally, up to 80% of lesions have decreased pigmentation and around 25% may be completely amelanotic. Many cases are already locally advanced at the time of diagnosis and the prognosis is overall quite poor, with the 5-year survival rate around 10-20%.

Case Description/Methods: This report presents a case of a 73-year-old Caucasian male with a past medical history of external hemorrhoids who presented to his primary care provider after developing rectal pain that did not resolve with sitz baths and over-the-counter topical therapy. A physical exam revealed three circumferential masses, believed to be hemorrhoids. The masses were then excised and sent for pathology, which revealed ARM with positive margins. Immunohistochemistry performed showed diffuse immunoreactivity for melan-A and SOX10 and negative for BRAF mutation. One month after diagnosis, the patient underwent abdominoperineal resection (APR) with colostomy followed by adjuvant therapy with pembrolizumab.

Discussion: This case highlights the importance for clinicians to express a high index of suspicion for ARM and should have a low threshold to biopsy suspicion lesions. The primary prognostic indicator for clinical outcomes is the stage at the time of diagnosis. Increasing awareness for ARM will hopefully improve the time to diagnosis and in turn, improve survival and quality of life.


Disclosures:


Gabrielle Sanford, MD¹, Jeremy Polman, DO, MS, MBA², Marshall Stagg, MD¹, Kelly Finan, MD³. E0143 - Hemorrhoid or Cancer: Anorectal Mucosal Melanoma Discovered During Hemorrhoidectomy, ACG 2022 Annual Scientific Meeting Abstracts. Charlotte, NC: American College of Gastroenterology.