NTRK1 and gastrointestinal stromal tumor: Interestingly, mRNA level of trkB ligands by qPCR analysis showed almost the same trend when they were examined in detail using RNA extracted from FFPE samples, although mRNA expression level of NTRK by Nanostring analysis was significantly higher in pan-trk/trkB positive group (Fig. 5, Supplementary Fig. 2) Furthermore, CNV analysis did not reveal amplification of NTRK2 in any of GIST cases (Supplementary Table 6).