A polynucleotide, which is a novel causative gene for cancer, is elucidated, and, based on this finding, provided are a method for detecting the polynucleotide, or a polypeptide encoded by the polynucleotide； a kit and a primer set for the detection； a method for screening an inhibitor of the polypeptide； and a pharmaceutical composition for treating a cancer containing the inhibitor. In the detection method of the present invention, an FGFR3 fusion protein, or a fusion gene encoding the fusion protein, or a TACC3 fusion protein, or a fusion gene encoding the fusion protein, is detected in a sample derived from female genitalia obtained from a subject.
