Severely dysplastic nevus: atypical Spitz nevus or melanoma in situ?

A 31-year-old patient presented with a new, rapidly growing pigmented skin tumor on her left thigh. Several years previously a level 2 superficial spreading melanoma (SSM) with a tumor thickness of 0.45 mm had been removed from her left thigh. Dermatoscopic examination revealed asymmetric pigmentation of the tumor with branched streaks of variable thickness and irregular pseudopodia. Histological analysis showed it to be a severely dysplastic melanocytic nevus.