De novo vs nevus-associated melanomas: differences in aggressiveness noted

June 18, 2015

Abstract

Background
Although 20%-30% of melanomas may be histopathologically “nevus-associated,” implying direct transformation of a nevus into melanoma, the majority of melanomas arise in clinically normal skin with no detectable precursor lesion. We aimed to determine whether nevus-associated and de novo melanomas differ in their associations with histopathologic features and survival.

Methods
1,048 melanoma patients prospectively enrolled in the NYU Melanoma Cooperative Group registry between 1972 and 1982 (NYU1) were analyzed to detect associations between type of melanoma (de novo vs nevus-associated) and age, anatomic site, ulceration, thickness, mitotic index, histological type, stage, and survival. We tested the significant associations in a replication cohort of 1,202 melanoma patients prospectively enrolled between 2002 and 2009 in the NYU Interdisciplinary Melanoma Cooperative Group registry (NYU2).

Results
In the NYU1 dataset, de novo melanomas were more likely to be associated with older age (54 vs 47 years, p < 0.01), non-axial location (OR 1.53, p < 0.01), tumor thickness > 1.0mm (OR 1.95, p < 0.01), ulceration (OR 1.61, p = .026), nodular subtype (OR 2.79, p < 0.01), stage > 1 (OR 2.35, p < 0.01), and shorter overall survival (p < 0.01). In the NYU2 replication dataset, de novo melanoma was again significantly associated with older age (61 vs 54 years, p < 0.01), non-axial location (OR 2.29, p < 0.01), tumor thickness > 1.0mm (OR 2.22, p < 0.01), ulceration (OR 2.92 p < 0.01), nodular subtype (OR 2.23, p < 0.01), stage > 1 (OR 2.43, p < 0.01), and shorter overall survival (p < 0.01). In multivariate analysis, de novo histopathology was an independent, poor prognostic indicator in the NYU2 cohort only (HR = 1.69, p < 0.01). The NYU2 cohort has patients with thinner tumors (56.2% have tumors < 1.0mm) compared to the NYU1 cohort (41.8% have tumors < 1.0mm), which may contribute to the differing impact of the de novo histopathology on the survival models for these cohorts.

Conclusions
These data suggest that de novo melanomas may be more aggressive than nevus-associated melanomas, and may differ in their molecular pathogenesis. These findings may also have implications for early detection programs.

Cymerman, RM, et al. De novo versus nevus-associated melanomas: Differences in associations with prognostic indicators and survival. J Clin Oncol 33, 2015 (suppl; abstr 9025) (ASCO Poster Session) http://meetinglibrary.asco.org/content/144413-156