Melanoma in situ mimicking a lichen planus-like keratosis

The incidence of melanoma has steadily increased over the past three decades. Melanoma in situ (MIS), defined as melanoma that is limited to the epidermis, contributes to a disproportionately high percentage of this rising incidence. Amelanotic melanoma presents as an erythematous macule or plaque and may initially be misdiagnosed as an inflammatory disorder. We report a case of amelonatic MIS raised on non-sun-exposed skin, inducing a lichen planuslike keratosis as inflammatory reaction, which clinically masked the melanoma.