Among the cancer types, urothelial cancer, carcinoma of unknown primary, non–small cell lung cancer, pancreatic exocrine cancer, and breast cancer had the highest number of patients with FGFR2 or FGFR3 alterations (urothelial cancer, 4064 of 17 670 patients [23.0%]; carcinoma of unknown primary sites, 2708 of 45 140 [6.0%]; non–small cell lung cancer 2140 of 142 670 [1.9%]; pancreatic exocrine cancer, 1601 of 45 750 [3.5%]; breast cancer, 1310 of 42 260 [3.1%]). This evidence concerns the gene FGFR3 and breast carcinoma.