Beyond the self-renewal and differentiation capabilities, I-type cells are associated with tumor relapse/metastasis[69], possess high tumor-forming capacity in vivo[70], and are characterized by overexpression of stemness-related molecules, including cluster of differentiation 133 (CD133), cKIT, NOTCH 1, GPCR class C group 5 member C (GPRC5C), and tropomyosin receptor kinase B (TRKB)[71]. Here, NTRK2 is linked to neoplasm.