ROS1 and spitz nevus: Thus, a study carried out on 140 spitzoid tumors reported the frequent occurrence of kinase fusions in spitzoid neoplasms, involving ROS1, Anaplastic Lymphoma Kinase (ALK), BRAF, RET, and Neurotrophic Receptor Tyrosine Kinase (NTRK1) [100]; the ROS1, ALK, and BRAF fusions are more frequent in Spitz nevus and AST than in Spitz melanoma; in contrast, NTRK1 fusions are more frequent in Spitz melanoma than in Spitz nevis and AST [100].