Amelanotic melanoma: Clinical presentation, diagnosis, and management

Abstract

Amelanotic melanoma (AM) is a subtype of cutaneous melanoma with little or no pigment on visual or histopathologic examination and accounts for approximately 2% of melanoma cases. This uncommon variant is often misdiagnosed or diagnosed in late stages due to its variable clinical presentation and lack of established criteria for clinical diagnosis. AM often presents nonspecifically as a pink to red macule, papule, or dermal nodule; therefore, dermatoscopy and reflectance confocal microscopy are extremely helpful tools in the diagnosis of AM. Histopathologically, there is an attenuation or complete absence of melanin granules, and immunohistochemistry for melanocytic markers, such as S100, Melan-A, and HMB-45, may be necessary for accurate diagnosis. Like other types of melanomas, the Breslow depth, presence or absence of ulceration, and mitotic rate are necessary for diagnosis, staging, and management. The standard of treatment for AM includes surgical excision with margins based on staging with sentinel lymph node biopsy, if indicated. We present the clinical and histopathologic features, special techniques, differential diagnosis, and current management of AM.