By Gary M. White, MD
An amelanotic melanoma (AMM) is a melanoma devoid of pigment. The correct diagnosis may not be suspected early on. This is why all lesions presumed to be pyogenic granulomas should be sent for histologic examination. Sometimes, an AMM may resemble a basal cell carcinoma. The AMM typically occurs in adulthood with a peak incidence in the fifth decade. They most commonly occur in the sun-exposed areas.
- AMM represents a significant problem in terms of patient education and screening for melanoma as it does not fit the classic ABCDE criteria.
- One study found AMMs grow 6 times faster than pigmented melanomas [JAAD 2014;71;691-7].
- Factors associated with increase risk of developing an AMM in one study [JAMA Derm 2017;153;1026] included the absence of back nevi, presence of many freckles, a sun-sensitive phenotypic index and prior AMM.
The lesion typically is a relatively rapidly growing pink, red or vascular-appearing papulonodule. ("When you see pink, stop and think"). Early lesions are often pink, symmetric and non-descript. Larger lesions often ulcerate or bleed. At times, there is a telltale bit of pigment at the base.
Dermoscopy of Amelanotic Melanoma
- Many shades of pink
- Many dotted, serpentine or linear vessels.
The treatment is the same as for melanoma. On average, prognosis is worse compared to classic melanoma because of the more rapid growth, delay in diagnosis, and, therefore, greater thickness of the lesion. However, the prognosis is no different than for a conventional melanoma given the same thickness and location, etc.
Amelanotic melanoma in the scalp.
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