An 50-year-old woman was concerned about the recent appearance of a small dark spot on the forehead. She denied trauma to the affected area, and was not taking medication.
Key point: The differential diagnosis of a blue-black macule such as this includes both malignant (melanoma) and benign (blue nevus, angioma) tumors, as well as dyschromia from exogenous factors (minocycline administration, traumatic graphite tattoo). A biopsy is mandatory in this case to establish the correct diagnosis.
Treatment: A conservative excisional biopsy (using a 4-mm punch) was done. The lesion proved to be a benign blue nevus.
Note: This type of nevocellular neoplasm appears blue because of the reflective and refractive properties of the considerable dermal melanin that is present. Such lesions only exceptionally transform into malignant tumors.