Primary Malignant Melanoma of the Oropharynx: A Rare Case of a Tonsillar Melanotic Lesion

Oral malignant melanoma (OMM) is a rare and aggressive malignancy arising from melanocytes in the oral mucosa. We present the case of a 33-year-old Ethiopian female who arrived at the ED with hematemesis, active oral bleeding, and a sensation of suffocation. On examination, a darkly pigmented, ulcerated mass was identified arising from the left posterior tonsillar pillar. Emergency surgery was performed to control the bleeding, and subsequent histopathological analysis confirmed a diagnosis of amelanotic malignant melanoma, supported by immunohistochemical positivity for S100, HMB45, Melan-A, and P16. Advanced imaging with PET-CT and MRI demonstrated a localized tumor without evidence of lymph node involvement or distant metastasis. The patient was treated with neoadjuvant immunotherapy using pembrolizumab, followed by curative-intent radiation therapy targeting high-risk mucosal regions and bilateral cervical nodes. She tolerated the treatment well, though she experienced radiation-induced mucositis, dermatitis, and weight loss. Immunotherapy was resumed post-radiation, and the patient has since completed ten cycles without significant immune-related adverse events. The rarity of OMM and its aggressive clinical behavior underscore the need for heightened clinical suspicion for pigmented or ulcerated oral lesions. This case illustrates the diagnostic and therapeutic complexities of primary oropharyngeal melanoma, especially in the context of amelanotic presentation. It emphasizes the importance of prompt multidisciplinary evaluation, integration of advanced imaging modalities, immunohistochemical profiling, and emerging immunotherapeutic strategies to improve patient outcomes.