ABSTRACT INTRODUCTION Anorectal malignant melanoma (ARMM) is a rare and aggressive neoplasm accounting for 0.5% of anal canal cancers, with an overall incidence of 0.4% worldwide. Due to its rarity, local data remain scarce. MAIN CONCERNS AND CLINICAL FINDINGS This case series discusses two elderly Filipinos with ARMM, both presenting as hematochezia and anorectal discomfort. Case 1 involved a 73-year-old female with a six-month history of intermittent bleeding and constipation. Case 2 involved a 77-year-old male with a history of stage I colon cancer, with a three-week history of painful defecation and rectal bleeding. Both patients observed a pigmented protruding rectal mass they initially attributed to hemorrhoids. PRIMARY DIAGNOSIS, INTERVENTIONS, AND OUTCOMES Colonoscopy, biopsy, and immunohistochemistry revealed ARMM in both cases. Case 1 had hepatic metastasis. She underwent wide local excision followed by Nivolumab, with stable disease and ongoing active treatment. Case 2 had widespread metastasis to lungs, liver, and bone. After surgical excision, he was treated with Pembrolizumab which was later on shifted to Imatinib. Despite aggressive intervention, disease progressed, and patient expired one year after diagnosis. CONCLUSION This case series highlights maintaining a high index of suspicion for malignancy in elderly patients with anorectal symptoms. Prompt biopsy, immunohistochemical evaluation, and multidisciplinary approach are critical to reduce diagnostic delays and enabling timely, individualized treatment. Increased awareness on ARMM, even in regions where it is rarely reported, will improve clinical outcomes.
Quebec et al. (Thu,) studied this question.