P0222 - Melanoma Where the Sun Doesn’t Shine

Shalini S. Jain, MD¹, William Reiche, MD¹, Jonathan Gapp, MD¹, Yazan Addasi, MD², Omar Alaber, MD², Sandeep Mukherjee, MD^3
1Creighton University, Omaha, NE; ²Creighton University Medical Center, Omaha, NE; ³CHI Health, Omaha, NE

Introduction: Anorectal melanoma is associated with a poor prognosis and a five year survival rate of 6-22%. It only accounts for 0.4% to 1.6% of all types of malignant melanoma. Late diagnosis occurs due to its location and nonspecific symptoms. It can be misdiagnosed since colonoscopy evaluation of the anorectum can be poorly visualized. We present a patient with anorectal melanoma to highlight the importance of keeping this malignancy in mind as part of the differential diagnosis for hematochezia.

Case Description/Methods: An 80-year-old male with a past medical history of hypothyroidism, diverticulitis, epilepsy, and coronary artery disease presented with intermittent rectal bleeding for six weeks. Patient denied abdominal or rectal pain. During colonoscopy, a hard ulcerated mass was palpated on rectal exam and visualized in the left anal canal region, extending from the perianal skin into the anal canal and involving 50% of the circumference of the rectum. Biopsies of the rectal mass were positive for malignant melanoma. Patient was considered a poor surgical candidate for resection given his age, comorbidities, and location of the tumor (involvement of sphincter musculature). CT/ PET scan revealed bilateral inguinal lymph node metastasis and BRAF testing was positive. A trial of immunotherapy with Nivolumab for four weeks was initiated. During this time, he developed a metastasis to the femoral neck extending over 80% of the femoral neck width. Immunotherapy was stopped. The patient ultimately was transitioned to hospice and passed away one year after his original date of diagnosis.

Discussion: Anorectal melanoma is often overlooked as a differential diagnosis for hematochezia. Since melanoma is a common cutaneous malignancy found in sun-affected regions, the anorectum tends to be forgotten. It is considered rare, and patients tend to have large lesions at the time of presentation. During a diagnostic colonoscopy for evaluation of hematochezia, clinicians often look for adenocarcinoma, which tends to appear as a fungating mass in the colonic lumen. The anorectal canal can be difficult to assess, both on external physical exam and colonoscopy. We aim to highlight the importance of practitioners looking closely at the anorectum and keeping a broad differential in mind for the patient that presents with bright red blood per rectum. Keeping a high index of suspicion for this malignancy can make a difference in the overall outcome of this highly aggressive and rare type of melanoma.



Disclosures:


Shalini S. Jain, MD¹, William Reiche, MD¹, Jonathan Gapp, MD¹, Yazan Addasi, MD², Omar Alaber, MD², Sandeep Mukherjee, MD³. P0222 - Melanoma Where the Sun Doesn’t Shine, ACG 2021 Annual Scientific Meeting Abstracts. Las Vegas, Nevada: American College of Gastroenterology.