Cutaneous melanoma associated with naevi prevalence: A 15-year cross-sectional retrospective study

Background/Objectives Melanoma may develop de novo or naevus associated (NAM). The exact prevalence and features of NAM are not fully elucidated. Methods A 15-year cross-sectional retrospective study was performed of all melanoma cases diagnosed and treated at the skin cancer centre of the University of Naples Federico II from September 2003 to August 2018. Data collected included patient's age, gender, melanoma anatomic site, Breslow thickness, and histolopathology including melanoma-associated lesion characteristics. Results A total of 1986 melanomas were included in the study. Based on histolopathogical examination, NAM represented 8.4% (n = 167) with de novo melanoma representing the great majority of the melanomas (91.6%). NAM was significantly more common in younger age compared to de novo melamoma (mean age 48 +/- 14.9 vs 54.3 +/- 15.9 years, P < 0.001), and more frequently involved the trunk (62.3% vs 51.8% P = 0.01). Mean Breslow thickness was significantly higher in de novo melanoma compared to NAM (0.97 +/- 1.48 mm vs 0.83 +/- 0.95, P < 0.001). However, in situ melanoma was more commonly observed in de novo melanoma (n = 640, 35.2%) rather than NAM (n = 41, 24.5%; P < 0.01) whereas invasive melanoma represented 75.5% (n = 126) of NAM and 64.8% (n = 1179) of de novo melanoma, P < 0.01. Conclusions NAM represent a small percentage of melanomas (8.4%) compared to de novo melanoma. NAM appeared to be significantly more common in younger age and more frequently involved the trunk, being associated with an overall better prognosis, due to a lower mean Breslow thickness respect to de novo melanoma.