“…Trauma may promote the development of extremity melanoma [1,6,7] Gender Men may have a worse prognosis compared to women [4,27,16,93,21,20] Anatomic subsite The poorer prognosis of AM might be more closely related to the anatomical site than the histological subtype [5,22,29,28,31] Molecular pathology characteristics Chromosomal structural variations and copy number variations Compared to CM, AM has more chromosomal structural variations and CNVs Common copy number amplified genes include CCND1, GAB2, PAK1, TERT, YAP1, MDM2, CDK4, NOTCH2, KIT, and EP300; common copy number deletion regions, including those containing CDKN2A and NF1 and PTEN [23,44,46,51,47,61] Driver mutations the proportion of TWT mutations is higher in AM than in CM (38% vs. 11%) [60] Immune microenvironmental characteristics TILs AM has a suppressive immune microenvironment compared to CM (CD 8 + T cell, NK cells, and γδ T cells) [80,84] M2-Ms the density of M2-Ms is higher in the ALM tumor microenvironment compared to SSM [85] PD-L1 Lower levels of PD-L1 are present in AM than in chronic sun-damaged melanoma (31% vs. 62%)…”