Blue naevus with satellitosis mimicking malignant melanoma.

Blue naevus is an acquired benign melanocytic naevus. It is a firm, sharply defined dark blue to grey-black papule or nodule, which is likely to arise from the arrested dermal melanocytes in the dermis. In the last few years, blue naevus has attracted much attention due to the recognition of new entities and to its confusion with malignant melanoma. We report a 69-year-old man who developed a blue-black nodular lesion with satellitosis on his scalp. Although clinically it was thought to be a malignant melanoma, histopathological investigation and conservative methods such as dermatoscopy and power Doppler ultrasonography did not confirm this diagnosis. Histopathological examination excluded malignant melanoma, as there were no cellular atypia and mitotic activity in either the nodular lesion or the satellitosis. Doppler ultrasonography confirmed the benign nature of the lesion. Dermatoscopic examination showed homogeneous steel-blue pigmentation with individual blue globules, dots and some brown veils, and confirmed the histopathological diagnosis. To the best of our knowledge, our case is the third reported case of a blue naevus with satellitosis mimicking malignant melanoma.