Persistent blue nevus simulating melanoma.

We report a case of a persistent blue nevus that significantly extended beyond the scar of the original excision mimicking those clinical changes usually seen in melanoma. The histopathologic evaluation revealed a common blue nevus. The lesion was re-excised, and 10 months later a bluish macule appeared next to the surgical scar. This case of a persistent blue nevus with an unusual clinical presentation and a benign clinical course highlights the fact that the clinical markers commonly used to identify melanoma in pigmented lesions will not always accurately diagnose melanoma.