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Many nevi, but lower melanoma risk associated with nevus-associated melanoma

Patients with more than 100 nevi and with an otherwise low risk for melanoma had a higher risk of developing nevus-associated melanomas, according to recently published study results.

Researchers conducted a prospective, observational study of 832 patients at high risk for melanoma. They documented melanoma risk factors, clinical and dermoscopic criteria of excised lesions and results of histopathologic examination. Evaluations took place between April 1, 1997, and May 31, 2012, with data analysis taking place between Sept. 1, 2012, and Dec. 31, 2013.

During the study period, 113 patients (62.8% men) were diagnosed with 190 melanomas (81in situ and 109 invasive). Invasive melanomas had a median Breslow thickness of 0.42 mm.

Remnants of melanocytic nevi were found in 103 melanomas (54.2%), according to histopathologic examination results. The trunk was the location of 65.1% of nevus-associated melanomas, but there was no statistical significance for the localization.

Patients with lower melanoma risk, defined as more than 50 common and/or ≤3 atypical nevi, (OR = 2.75; 95% CI, 1.14-6.64), patients with more than 100 nevi (OR = 1.63; 95% CI, 1.02-3.60) and patients with in situ melanoma (OR = 14.01; 95% CI, 6.14-31.96) had significantly more nevus-associated melanomas, according to univariate analysis. Patients with one or more previous melanomas had significantly less frequent nevus-associated melanomas (OR = 0.28; 95% CI, 0.21-0.83).

There was no significant influence on nevus-associated melanoma manifestations when other factors were measured, including age, skin type, hair color and melanoma thickness.

“Multivariate regression analysis identified three independent patient-related factors (high nevus count, low risk for melanoma and female sex) and one melanoma-related factor (in situ melanoma) to be indicative of a significantly increased probability of nevus-associated melanomas,” the researchers wrote.

“We were able to demonstrate that patients who develop nevus-associated melanomas show a distinct risk profile that differs from that of patients with de novo melanomas,” the researchers concluded. “Patients with many acquired nevi on the trunk appear to be at high risk for developing nevus-associated melanomas and may, therefore, particularly benefit from sequential digital dermoscopy in addition to total-body photography.”  – by Bruce Thiel

Disclosure: The researchers report no relevant financial disclosures.