This article is more than 5 years old. Information may no longer be current.

One-third of melanomas develop from preexisting nevus

Nevus-associated melanomas accounted for approximately one-third of all melanomas found in a recent systematic review and meta-analysis.

Researchers reviewed findings from 38 observational cohort and case control studies comprising 20,126 melanomas. The ratio of nevus-associated melanomas served as the primary outcome measure. Thickness of nevus-associated melanoma, nevus-type and overall survival served as secondary endpoints.

Results indicated that 5,852 (29%) of the melanomas were nevus-associated, while 70.9% were de novo malignancies. The likelihood of any given melanoma being nevus-associated was less than 65% (RR = 0.36; P < .001). The researchers noted heterogeneity between studies for this finding.

Analysis of Breslow thickness revealed that nevus-associated melanomas were significantly less thick than de novo malignancies (mean difference, –0.39 mm; P = .0003). These findings were culled from eight studies that had detailed information about Breslow thickness in nevus-associated and de novo melanomas.

The investigators observed no associations in terms of nevus-associated malignancies distribution of dysplastic or non-dysplastic nevi (RR = 0.77; P = .24), according to the findings.

Nevus-associated melanomas comprised 47.3% of melanomas among patients aged 60 to 69 years, 33.5% of those aged 70 to 79 years, and 19.2% of those aged 80 to 89 years.

Only two studies contained overall survival information for nevus-associated and de novo melanomas. Analysis of these two data sets revealed a slight survival advantage in the nevus-associated group.

Among all nevus-associated melanomas, 77.4% were acquired and 22.6% were congenital. When the researchers excluded congenital malignancies, intradermal nevi accounted for 54% of malignancies, whereas 21.7% were junctional and 15.4% were compound remnants.

“This result provides further evidence that most melanomas do not originate from malignant transformation of nevus cells,” the researchers concluded. “The question of

whether [nevus-associated melanoma] is a result of a malignant transformation of nevus cells cannot be elucidated by the findings of the present meta-analysis.” – by Rob Volansky

Disclosure: The researchers report no relevant financial disclosures.