FGFR1 and cancer: FGFR1 SNVs are rare and have been reported in fewer cases of cancer in comparison with FGFR2 and FGFR3. The two most common activating mutations in FGFR1 are N546K and K656E, both of which reside in the kinase domain and result in increased kinase activation and transformation in vitro.3,14–16 Although the functional consequence is unknown, the S125L mutation has been reported in both breast and gallbladder cancer.17,18