Dermoscopy of Amelanotic Melanoma

Overview / Definition Amelanotic melanoma (AM) is defined as a type of melanoma that lacks the characteristic brown or black pigment typically associated with melanoma, resulting in a pink, red, or skin-colored appearance. This variant can often be misdiagnosed due to its atypical clinical features, leading to delays in treatment. Epidemiology Amelanotic melanoma accounts for approximately 2% to 8% of all melanoma cases. It is more common in individuals with fair skin and those who have a history of sun exposure. The incidence is increasing, particularly among older adults. Higher prevalence in older adults. Affects both genders, but may be more common in men. Increased incidence in fair-skinned individuals. Pathophysiology / Mechanism The pathophysiology of amelanotic melanoma involves the malignant transformation of melanocytes, where genetic mutations lead to uncontrolled cellular proliferation. The absence of melanin may be due to factors such as decreased tyrosinase activity or mutations affecting the melanin synthesis pathway. Common mutations include BRAF, NRAS, and TP53. Melanocyte transformation is influenced by UV radiation and other environmental factors. Clinical Presentation Clinically, amelanotic melanoma can present as a variety of lesions, often resembling benign conditions such as pyogenic granulomas, basal cell carcinoma, or other non-melanocytic tumors. Key features include: Color: Lacks pigment, may appear pink, red, or colorless. Shape: Can be irregularly shaped or asymmetrical. Size: Typically larger than 6 mm, but not always. Surface: May have ulceration or crusting. Diagnosis / Workup Dermoscopy is an essential tool in the diagnosis of amelanotic melanoma. The dermoscopic features often include: Vascular structures: May show atypical vasculature, including dotted or linear vessels. Irregular pigmentation: Even in the absence of color, irregular or subtle pigmentation may be observed. Background: A pink or red background may indicate malignanc