Favorable prognosis for malignant melanomas associated with acquired melanocytic nevi

Abstract

In a clinicohistopathologic study of 557 patients with primary cutaneous malignant melanoma, there were fewer metastases and/or deaths from melanoma when histologic evidence of a coexisting acquired melanocytic nevus was found. A total of 130 patients with melanocytic nevus and 427 cases of melanoma without histologic evidence of a nevus (denovo) were studied. Clinical follow-up evaluation for evidence of metastases and/or death was obtained. Only 10 of the patients (7.7%) with nevus-associated melanoma had metastases and/or death vs. 78 (18.3%) with de novo melanoma. When stratified by lesion thickness, the logrank test for survival revealed a statistically significant difference between the 2 groups. An overall favorable outcome seen in patients with malignant melanomas associated with acquired melanocytic nevi was found, therefore, to be independent of lesion thickness and 6 other variables reported to be related to the biologic behavior of malignant melanoma. Thus, the presence of nevus cells in a specimen of malignant melanoma portends a better prognosis and may have important implications in the biology of this neoplasm.