Amelanotic melanoma.

Cutaneous amelanotic melanoma (AM) is a rare amelanotic or a hypomelanotic subtype of melanoma, comprising only 0.4-27.5% of all melanoma cases. The mean age of the patients is over 50 years, and the male/female ratio varies from 0.5 to 4. Patients with red hair, type I skin, freckles, lack of nevi on the back, a sun-sensitive phenotype, or previous AM history are more likely to develop AMs. As AMs lack pigmentation, their appearances vary and can mimic many benign and malignant conditions, thus presenting a diagnostic challenge. AMs are composed of greater proportions of nodular melanoma, acral lentiginous melanoma, and desmoplastic melanoma than pigmented melanomas. They also present with thicker Breslow thickness, higher mitotic rate, more frequent ulceration, higher tumor stage, and lower survival than pigmented melanomas.