The presence of dysplastic nevus remnants in malignant melanomas. A population-based study of 551 malignant melanomas.

We examined 512 malignant melanomas, representing all newly diagnosed cutaneous malignant melanomas, excluding lentigo maligna melanomas, from the period October 1, 1982 to March 31, 1985 occurring in the region of eastern Denmark in patients aged 20-79 years for the presence of dysplastic nevus remnants. Criteria for the diagnosis of a dysplastic nevus remnant include all the following changes (a) lentiginous or epithelioid melanocyte hyperplasia, (b) cytologic melanocyte atypia, (c) eosinophilic fibroplasia, (d) lamellar fibroplasia, and (e) lymphocytic infiltration in the dermis. Dysplastic nevus remnants were found in association with 34 (7%) of the evaluable 512 malignant melanomas. Fourteen (41%) of the remnants were of compound nevus type. In nine (27%) of the remnants, atypia was pronounced. Most (62%) dysplastic nevus remnants were contiguous to thin superficial spreading melanomas. We conclude from this population-based study that about 7% of malignant melanomas arise in prior dysplastic nevi.