Clinicopathological, Genetic and Survival Advantages of Naevus-associated Melanomas: A Cohort Study.

Abstract

Several studies have suggested that naevus-associated melanomas differ from de novo melanomas, being thinner and with less ulceration; however, the prognostic implication is unclear. The objective of this study was to describe clinicopathological, genetic and survival characteristics of de novo and naevus-associated melanomas in a cohort of primary invasive cutaneous melanomas over a 20-year period. Of the 2,227 patients included in the study, 509 (22.86%) had naevus-associated melanomas. Compared with patients with de novo melanoma, they were younger, with a fairer phototype and a higher naevus count, tumours were predominantly the superficial spreading subtype, American Joint Committee on Cancer stage I, located on the trunk, and there were fewer signs of invasiveness (thinner Breslow index, less ulceration, lower mitotic index and less satellitosis). Germline mutational status did not show any significant association. As determined through univariate analysis, overall survival was significantly better in patients with naevus-associated melanoma (hazard ratio 0.64; 95% confidence interval 0.51–0.80, p < 0.001), but multivariate analysis did not support this prognostic indication (hazard ratio 0.94; 95% confidence interval 0.75–1.18, p < 0.606). Despite this, we conclude that naevus-associated and de novo melanomas should be considered as different subtypes of melanoma.