Nevi are among the strongest risk factors for melanoma. However, little is known about the association of many total nevi (TN) or atypical nevi (AN) with tumor thickness.
To examine the association between age and the number of TN and AN and to explore whether there was a relationship between TN or AN and tumor thickness, controlling for multiple variables.
Design, Setting, and Participants
Survey of patients with melanoma at 2 academic sites and an affiliated Veteran Affairs medical center. Participants included 566 patients surveyed within 3 months of diagnosis. Patients were surveyed in the melanoma clinics from May 17, 2006, through March 31, 2009, within 3 months of diagnostic biopsy. The dates of the analysis were April 1, 2015, to August 1, 2015.
Main Outcomes and Measures
Counts of TN and AN were performed at the first visit after diagnosis and were categorized as 0 to 20, 20 to 50, or more than 50 for TN and as 0, 1 to 5, or more than 5 for AN. Tumor thickness was categorized as 2.00 mm or less or as 2.01 mm or greater. All analyses were stratified by patient age (<60 or ≥60 years). Logistic regression was used to test associations, controlling for age, sex, anatomic location of melanoma, institution, histologic subtype, marital status, performance of skin self-examination, number of health care visits in the past year, mode of melanoma discovery, and receipt of skin examination by a physician.
The study population included 566 patients. Their mean (SD) age was 56.7 (15.9) years, and 39.0% (n = 221) were female. Of 566 patients, the number of TN was classified as 0 to 20 (66.4% [n = 376]), 20 to 50 (20.5% [n = 116]), or more than 50 (13.1% [n = 74]). Atypical nevus counts were 0 (73.3% [n = 415]), 1 to 5 (14.5% [n = 82]), or more than 5 (12.2% [n = 69]). For those younger than 60 years, the presence of more than 50 TN was associated with a sharply reduced risk of thick melanoma (odds ratio, 0.32; 95% CI, 0.12-0.81), and the presence of more than 5 AN compared with no AN was associated with thicker melanoma (odds ratio, 2.43; 95% CI, 1.02-5.75).
Conclusions and Relevance
Most patients with melanoma had few nevi and no AN. In younger patients (<60 years), thick melanomas were commonly found in those with fewer TN but more AN, suggesting that physicians and patients should not rely on the total nevus count as a sole reason to perform skin examinations or to determine a patient’s at-risk status. Younger patients should be educated on the increased risk of thicker melanomas that is associated with having more AN.