NEW YORK – Consistent with another recently published report but counterintuitive, patients with a high number of nevi prior to developing a melanoma have more favorable prognostic features than do those with fewer moles, according to data presented at the American Academy of Dermatology summer meeting.
Based on differences in numerous clinicopathologic features when patients with more than 50 nevi were compared with those with fewer than 50 nevi, “It is possible that there are different pathways that drive melanoma in these two patient groups, resulting in different degrees of aggressiveness,” reported Dr. Caroline Kim from the Pigmented Lesion Clinic and Cutaneous Oncology Program, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston.
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In this study of 281 melanoma patients evaluated over 2 years at Dr. Kim’s clinic, those with a high nevi count (89 patients) were compared with those with a lower nevi count (192 patients). The investigators also performed comparisons on those who had dysplastic versus nondysplastic nevi. Of differences between the groups, the initial melanoma grade was the most surprising.
In the greater-than-50-nevi group, 21.6% had either stage III (18.2%) or stage IV (3.4%) disease at diagnosis vs. 40.2% in the fewer-than-50-nevi group (31.2% and 9.0% with stage III and IV disease, respectively). Conversely, melanoma was diagnosed at stage I in 71.6% in the greater-than-50-nevi group vs. only 41.8% in the fewer-than-50-nevi group.
Among patients in the fewer-than-50-nevi group, ulceration was more common (25.1% vs. 10.3%; P = .017) as was nodular subtype (11.2% vs. 2.9%; P = .035). The group with the lower nevi count also had a higher mitotic rate (3.7 vs. 2.3 count/mm2) and a greater Breslow’s depth (1.78 vs. 1.21 mm; P = .010). Although not significantly different, the proportion of females was higher in the lower nevi count group (56.2% vs. 46.4%) and more patients in this group developed a melanoma in the head or neck (21.6% vs. 15.3%).
There are several potential explanations for the differences observed in this study. One is that the process that drives a high nevi count is different than that which produces lower numbers of nevi. According to Dr. Kim, some of the pathologic features in the greater-than-50-nevi group were more consistent with BRAF mutation patterns than the fewer-than- 50-nevi group. Another is that a high nevi count drives a more robust immune response against melanoma growth. Dr. Kim cited published studies that support both theories.
However, it is also possible that high nevi count increases likelihood of dermatologic care and vigilance for early detection of melanomas. This might be supported by the fact that the age of diagnosis was significantly younger in the greater-than-50-nevi count group (40.1 vs. 50.1 years; P less than .001). However, a younger age at diagnosis could also be a product of different pathways of disease development and growth.
The greater likelihood of more aggressive melanoma in patients with a history of fewer than 50 nevi than in those with greater than 50 nevi has also been supported by another large series that was recently published (Int J Cancer. 2015 Oct 1;137[7]:1691-8.) Cited by Dr. Kim as consistent with her own findings, this study of 2,184 melanoma cases compared 5- and 10-year survival in those who had greater than 50 nevi, which represented 31.3% of this population, to those with fewer. The greater survival at 5 years in the greater-than-50-nevi group (91.2% vs. 86.4%) and 10 years (87.2% vs. 79%) remained significant after adjusting “for all known melanoma prognostic factors,” according to the authors.
Further studies evaluating differences in patterns of melanoma growth in those with fewer than 50 nevi vs. those with more are needed, according to Dr. Kim. She acknowledged that one limitation of her study was that all cases were drawn from a single center. However, there is support for an independent study, and the findings, if verified, “have major implications for public health screening and education.” In particular, she suggested that those with lower nevi counts might deserve the type of attention already being directed at those with high nevi counts “as they may be paradoxically at risk for more aggressive melanomas.”
Dr. Kim reported financial relationships with Hoffman-LaRoche, Castle Biosciences, and Shape Pharmaceuticals.
This article was updated August 26, 2015.