Simultaneous melanomas in the setting of multiple primary melanomas

It is estimated that about 1–13% of melanoma patients will develop multiple primary melanomas. Although the occurrence of subsequent tumors has been described during the last few years, the development of simultaneous melanomas has not yet been extensively studied. We reviewed our registries to identify patients with multiple primary melanomas. We studied epidemiological, clinical, and histological characteristics of patients who were diagnosed with simultaneous melanomas and compared them with those of patients who developed non-synchronous multiple primary melanomas. As simultaneous were defined subsequent melanomas that were diagnosed either at the same visit or within a time-period of maximum of 1 month. Between 2000 and 2020, 2500 patients were diagnosed with melanoma at Andreas Syggros Hospital. 86 (3.4%) patients presented multiple primary melanomas and among them, 35 (40.7%) developed simultaneous melanomas. Patients with simultaneous melanomas developed more frequently more than 2 tumors. First tumors of patients with non-synchronous melanomas were significantly thicker than second tumors while those of patients with simultaneous melanomas did not differ significantly. Slight differences in the tumor localization, staging and histologic type were observed between the two groups. However significant differences were ascertained between first and second tumors in both groups. Simultaneous melanomas occupy an important proportion of multiple primary melanomas, affecting a non-negligible number of patients. Slight differences between simultaneous and non-synchronous multiple primary melanomas seem to define a distinct subcategory of multiple primary melanomas.