Amelanotic Nodular Melanoma Over the Knee Region: A Case Report of a Diagnostic Challenge From the United Arab Emirates

Amelanotic melanoma (AM) is a rare and aggressive subtype of cutaneous melanoma that lacks the characteristic pigmentation, which makes it challenging to diagnose, often resulting in delayed treatment. Nodular melanoma (NM), a subtype of AM, is associated with a poorer prognosis and is infrequently reported in the Middle East and North Africa (MENA) region. AM is a rare and aggressive subtype of cutaneous melanoma, accounting for approximately 1-8% of all melanoma cases. We present the case of a 39-year-old Filipino female with a slowly enlarging, skin-colored lesion on her right patella, initially misdiagnosed as a dermatofibroma. The lesion was later confirmed as type IIIb cutaneous amelanotic nodular melanoma via histopathology and immunohistochemistry, with a Breslow thickness of 5 mm and Clark level IV invasion. Sentinel lymph node biopsy revealed nodal involvement, and the patient underwent wide local excision followed by adjuvant immunotherapy. This report highlights the diagnostic challenges posed by AM, particularly in younger patients and in regions where such cases are rarely reported. Accurate diagnosis requires a high index of suspicion and a multimodal diagnostic approach. Early recognition and intervention are crucial for improving patient outcomes in this aggressive malignancy.