FGFR1 and neoplasm: Pemigatinib, an oral tyrosine kinase inhibitor, blocks fibroblast growth factor receptor 1, 2, and 3 (FGFR1-3) from binding its ligand FGF to prevent downstream signaling.8 FGFR has been implicated in several cellular proliferation and angiogenic pathways activating MAPK, PI3K, JAK/STAT, PLC signaling cascades, promoting epithelial to mesenchymal transformation, and fostering an immunosuppressive tumor microenvironment.9-11 Several mechanisms of FGF dysregulation have been recognized including amplifications, activating mutations, and fusions/translocations.