NTRK1 and neoplasm: The tumor cells were robustly and diffusely positive for Trk, S100-protein, CD34, and nestin (Figs. 4 and 5), but negative for CD56, SMA, desmin, myogenin, STAT6, EMA, CK, CD1a, CD21, CD35, CD43, WT-1(c-terminal), MelanA, HMB45, BRAF, and ALK.