High nevus counts confer a favorable prognosis in melanoma patients

Abstract

A high number of naevi is the most significant phenotypic risk factor for melanoma and is in part genetically determined. The number of naevi decreases from middle age onwards but this senescence can be delayed in melanoma patients. We investigated the effects of naevus number count on sentinel node status and melanoma survival in a large cohort of melanoma cases. Out of 2184 melanoma cases, 684 (31.3%) had a high naevus count (>50). High naevus counts were associated with favourable prognostic factors such as lower Breslow thickness, less ulceration and lower mitotic rate, despite adjustment for age. Naevus count was not predictive of sentinel node status. The crude 5- and 10-year melanoma specific survival rate was higher in melanomas cases with a high naevus count compared to those with a low naevus count (91.2% vs 86.4% and 87.2% vs 79%, respectively). The difference in survival remained significant after adjusting for all known melanoma prognostic factors (HR= 0.43, CI 0.21-0.89). The favourable prognostic value of a high naevus count was also seen within the positive sentinel node subgroup of patients (HR=0.22, CI 0.08-0.60). High naevus count is associated with a better melanoma survival, even in the subgroup of patients with positive sentinel lymph node. This suggests a different biological behaviour of melanoma tumours in patients with an excess of naevi.

Clinical and pathological melanoma differences in young and old people

“…3,5,7,8 MacDonald et al 7 found that melanoma was less likely to arise from a pre-existing naevi in patients older than 70 years. Although multiple naevi is a powerful predictive phenotypic marker for melanoma development, nevi usually involute after the 40 th decade; therefore, they are much less numerous in older patients, 9 thus explaining why we found significantly less elderly with more than 50 naevi. As a matter of fact, high nevus count have been recently associated with better disease specific survival, even within positive sentinel lymph node patients.…”

“…[3][4][5] The risk associated with sun exposure and multiple naevi, for example, are controversial. 8,9 Traditional prognostic factors for cutaneous MM include thickness, ulceration, mitoses/mm 2 , clinical stage, anatomic location, sex and age, 10 and although some pathologic features were previously linked to lower disease specific survival rates, 4,5,7,10 some associations remain uncertain in older patients. 10 In accordance to our findings, several studies suggested that melanoma is more common in older men; 3,4,6-8,10 they have focused on histologic features and/or survival, and few evaluated risk factors for melanoma.…”

Authors' reply to: High naevus counts confer a favourable prognosis in patients with melanoma

“…In our study, 1 we reported evidence for better survival in patients with melanoma with many naevi, suggesting that this might reflect a different biology in this subset of melanomas. Autier et al have suggested that an alternative explanation might be that the better survival observed in patients with many naevi may in fact result from a selection bias due to these tumours being discovered by screening.…”

“…There is published data which suggest that melanomas diagnosed in follow-up screening were unlikely to have been offered sentinel node biopsy and are therefore unlikely to have been included in our study. 1 In the Barcelona Melanoma Unit, melanomas diagnosed in patients undergoing screening were reported to be all Stage 0 or IA. 2 When using total body photography and digital dermoscopy, none of the 98 melanomas diagnosed during screening required sentinel lymph node biopsy in a mean follow-up of 98 months.…”

Re: High nevus counts confer a favorable prognosis in melanoma patients by S ribero and co‐workers, published in the International Journal of Cancer, 2015 (online 21 march 2015)

“…1 Number and size of nevi is the strongest risk factor for melanoma occurrence, and despite a lack of evidence, it is generally assumed that higher risk of melanoma occurrence would also mean a higher risk of melanoma death. Because of this assumption, subjects with high nevus count are recommended to have regular skin examinations so that detection of melanoma at an early stage may prevent the occurrence of late stage, potentially lethal melanoma.…”