Epidemiologic characteristics of de novo versus nevus-associated melanoma

The exact role of nevi in the development of melanoma is not yet completely understood, and it remains unknown whether de novo and nevus-associated melanoma (NAM) constitute distinct biological entities. A few studies have documented differences in histological and clinical characteristics between de novo and NAMs; however, data from Southern Europe are lacking. This study examined epidemiological and clinical data of patients who were followed up at the Melanoma Reference Center of the General Hospital of Athens G. Gennimatas from 2022 to 2024 and had been diagnosed with primary skin melanoma from 1999 to 2024. In a total of 509 primary melanomas 289 (56.8%) were nevus-associated and 220 (43.2%) de novo. NAMs were more likely to be diagnosed in patients <40 and 40-65 years old compared to de novo melanomas (P < 0.001). NAMs were more likely to develop on the trunk and the extremities compared to de novo tumors, which predominated on the head (P < 0.001). Superficial spreading melanomas were more likely to be nevus-associated, while nodular, acral lentiginous, and lentigo maligna melanomas were more likely to develop de novo (P < 0.001). NAMs were more likely to be diagnosed at earlier stages and be thinner compared to de novo tumors (P < 0.001). NAMs were also more likely not to present ulceration (P = 0.002) and to have a low mitotic rate (<3/mm2) (P < 0.001). Patients with de novo melanomas more often experienced disease progression compared to those with NAM. NAMs seem to have less aggressive behavior compared to de novo melanomas. This study highlights the differences between de novo and NAMs, adding novel information about features such as the presence of dysplastic nevi, the mitotic rate, and the disease progression that had not been investigated in previous studies.