Most patients with melanoma had few moles and no atypical moles, and in patients younger than 60, thick melanomas were more commonly found in those with fewer moles but more atypical moles, according to an article published online by JAMA Dermatology.

Studies have suggested that the number of total moles and atypical moles is associated with the risk of melanoma. Yet the relationship of those mole patterns with tumor thickness and cancer prognosis is complex.

Alan C. Geller, M.P.H., R.N., of the Harvard T.H. Chan School of Public Health, Boston, and coauthors looked at the association between age and total moles and atypical moles and whether there was a relationship between total moles or atypical moles and tumor thickness, a very important prognostic indicator for melanoma.

The study included 566 patients with melanoma and most of them (66.4 percent or 376) had zero to 20 total moles, while 73.3 percent (415 patients) had no atypical moles.

In patients younger than 60, having more than 50 total moles was associated with reduced risk for thick melanoma, while having more than five atypical moles compared with no atypical moles was associated with thicker melanoma, according to the results.

"Several public health messages emerge from our study, including that melanomas are more commonly diagnosed in individuals with fewer nevi compared with those with a high mole count. Therefore, 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," the study concludes.