Background: Atypical nevi (AN), present in either a familial or a sporadic setting, are strong indicators of increased melanoma risk.
Objective: To estimate the extent of this risk and the extent of reclassification of sporadic to familial cases during follow-up.
Methods: We studied 167 sporadic patients with AN (>or=5). At the end of follow-up we updated the family history regarding melanoma and performed germline mutation analysis of the known melanoma susceptibility genes.
Results: We found a relative risk for melanoma of 46.1 (95% confidence interval 21.0-87.5). Six of 167 patients were carriers of a CDKN2A mutation. At the end of follow-up, 10 of 136 patients with sporadic AN reported being a member of a melanoma family.
Limitations: This study was conducted in an area with a founder mutation in many of its melanoma families; therefore the results may not be applicable to other populations.
Conclusion: We report a high relative risk of 46.1 of melanoma development in patients with sporadic AN. A significant proportion of this Dutch cohort reported additional cases in their families over time.