Polynucleotides which are novel causative genes for cancer are elucidated, and a detection method of the polynucleotides or polypeptides encoded by the polynucleotides, and a kit and a primer set for detection are provided, based on the knowledge gained by the elucidation. In the detection method, a fusion gene comprising part of an SDC4, CD74, EZR, SLC34A2, LRIG3, or TPM3 gene and part of a ROS1 gene, or a fusion protein encoded by the fusion gene is detected. The primer set or the detection kit comprises a sense primer designed based on a portion encoding SDC4, CD74, EZR, SLC34A2, LRIG3, or TPM3 and an antisense primer designed based on a portion encoding ROS1.