To assess lentigo maligna (LM) as an epidemiological entity separate from other melanomas (OMs) in elderly people.
Double age- and sex-matched case-control study to compare the risk factors for LMs and OMs.
A total of 76 patients with LM were paired by age and sex with 76 patients with OMs and 152 controls.
Main Outcome Measures
The association of melanoma risk with the following potential risk factors: sun exposure history by 10-year periods, frequency of sunburns, phenotypic traits, density of freckles and sun sensitivity at age 20 years, counts of nevi larger than 2 mm in diameter on the face and forearm, skin aging features (as assessed using a photographic scale), and history of basal and/or squamous cell carcinomas.
Risk of LMs and OMs were similarly associated with history of sunburns, light skin type, and freckling. Cumulative chronic outdoor and occupational sun exposures were not risk factors in any of the 2 groups of melanomas. Lentigo maligna differed from OMs by the absence of a detectable association with the number of nevi and a greater association with nonmelanoma skin cancers.
Although chronically sun-exposed skin is a prerequisite for LM, risk of LM does not increase with the cumulative dose of sun exposure, but LM is associated with sunburn history, like all other types of melanomas. The main epidemiological characteristic of LM is the absence of an apparent relation with the genetic propensity to develop nevi. This epidemiological profile is in accordance with recent molecular findings and may also account for the histoclinical and evolutive characteristics of LM.