NTRK1 and neoplasm: The mechanism of natural regression is still unclear, but the following are considered to be associated with the spontaneous maturation of tumors: age <18 months, differentiation type, good INSS stage, non-MYCN amplification, TrkA expression, and apoptosis.[8] Therefore, it was theoretically speculated that the natural regression characteristics of the tumor were differentiated to some extent and resulted in good outcomes.