EP370 - Atypical Hemorrhoid or Hidden Malignancy? Anal Melanoma and Palliative Strategies

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Purpose/Background: Anal melanoma is a rare and aggressive malignancy with poor prognosis due to late detection and a high propensity for metastasis. Its presentation often mimics common anorectal conditions, such as hemorrhoids, leading to delays in diagnosis. Due to its rarity, timely identification and appropriate treatment are critical to improving patient outcomes and quality of life (QOL).

Methods/Interventions: ZY is a 60-year-old woman who presented with a palpable external mass which she attributed to being a hemorrhoid. Her symptoms included progressive enlargement, discomfort while sitting, moisture changes, and intermittent bleeding. She had no personal or family history of colorectal cancer (CRC) or skin malignancies, and her colonoscopy 9 months earlier had been normal. Physical examination revealed a melanotic, firm, nontender mass at the anal canal. A biopsy confirmed malignant melanoma. MRI revealed a 4.6cm exophytic anal mass, left inguinal metastatic lymph node and irregular pelvic side wall lymph node. A PET CT confirmed metastatic disease to the left inguinal nodes and the lungs.
The patient was started on induction immunotherapy with nivolumab and ipilimumab. Although her lesion improved in size, she continued to experience symptoms, including itching, discomfort, and intermittent bleeding impairing her ability to work. Given her significant symptoms and lack of curative options, local excision was recommended for palliation. She underwent excision of the redundant tumor portion with intentional positive margins to avoid sphincter damage. The patient tolerated the procedure well, with complete wound healing at follow-up.

Results/Outcomes: Historically, abdominoperineal resection (APR) was used for local control of anal melanoma. However, wide local excision (WLE) now offers comparable survival outcomes with less morbidity. Given the poor prognosis associated with metastatic anal melanoma, WLE is preferred, focusing on symptom relief and quality of life (QOL). In metastatic dermal malignancies, surgery is typically reserved for symptom palliation. In ZY's case, without radiation and under ongoing immunotherapy, the risk of a non-healing wound was considered low. Immunotherapy agents like nivolumab and ipilimumab enhances the immune response to cancer and can slow progression. Decision making regarding excision during ongoing immunotherapy was extrapolated from colleagues in the cutaneous melanoma space and case reports.

Conclusion/Discussion: Expeditious diagnosis of anorectal lesions is imperative to diagnosis of rare conditions such as anorectal melanoma. While surgical options include APR and WLE the contemporary improvements in overall survival lend to renewed consideration of surgical options in all stages of disease. This case demonstrates improved quality of life in the metastatic setting with combined immunotherapy and palliative excision.