Clinicians Should Not Rely On Total Mole Count To Determine Melanoma Risk

Researchers question the emphasis on high total and atypical nevus counts as indicators of melanoma risk and suggest that individuals with few nevi should also be monitored

medwireNews: Research published in JAMA Dermatology shows that most patients with melanoma do not have a high total or atypical nevi count.

“Our findings raise the question as to whether major public health messages overstate the emphasis on many [total nevi] or [atypical nevi] and suggest that at-risk patients and their health care professionals should be equally concerned about melanoma risk in those with few nevi”, the team writes.

Moreover, in patients aged 60 years or less, a higher mole count was associated with a reduced risk of thick melanomas while the presence of more than five atypical nevi versus none was linked to an increased risk.

The researchers speculate: “Thinner melanomas in patients with more [total nevi] might be due to a less aggressive biological behavior of melanoma and a tendency of these patients to have their moles checked more frequently, whereas having more [atypical nevi] may make discovery by either the patient or his or her physician more difficult because the true ‘outlier’ melanoma may be less easily recognized.”

Among 566 melanoma patients surveyed within 3 months of diagnosis, the majority (66.4%) had between 0 and 20 nevi, while 20.5% had between 20 and 50 nevi and 13.1% had more than 50. Furthermore, 73.3% of participants had no atypical nevi, while 14.5% had between one and five and 12.2% had more than five atypical nevi.

Multivariate analysis adjusting for confounders such as age, gender and histological subtype showed that for patients younger than 60 years, a total nevus count of more than 50 compared with a count of 0–20 was associated with a decreased risk of thick melanomas, defined as tumours with a thickness of 2.01 mm or greater, with an odds ratio (OR) of 0.35.

However, the risk of developing thick melanomas was increased for patients of this age who had more than five atypical nevi versus no atypical nevi, at an adjusted OR of 2.89.

These findings suggest 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”, say Alan Geller, from the Harvard T. H. Chan School of Public Health in Boston, Massachusetts, USA, and fellow investigators.

They add that “younger patients should be educated on the increased risk of thicker melanomas that is associated with having more [atypical nevi]”.

Among patients older than 60 years, neither total nor atypical nevus counts were associated with tumour thickness, the study authors report. But they believe that “this lack of a finding may be explained by the fact that there were only 10 patients 60 years or older with more than 50 nevi.”

Reference

Geller AC, Mayer JE, Sober AJ, et al. Total nevi, atypical nevi, and melanoma thickness. An analysis of 566 patients at 2 US centers. JAMA Dermatol 2016; Advance online publication 2 March. doi:10.1001/jamadermatol.2016.0027

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