Intra-epithelial changes in childhood nevi simulating malignant melanoma.

Upward epidermal spread by tumour cells is one of the features looked for in the diagnosis of malignant melanoma. Unusual changes--resembling invasion and destruction of the epidermis--in a nevus from a 5 yr-old boy largely contributed to an erroneous diagnosis of malignant melanoma from 2 of 4 expert dermatopathologists. A subsequent prospective 5 yr survey of benign melanocytic lesions at a pediatric hospital showed 14 of over 200 nevi with prominent upward intraepidermal nevus cell migration. "Invasion" appears to be at the extreme end of a spectrum of upward spread in childhood nevi and is probably seen only in children.