NTRK2 and neoplasm: Allen et al. have identified a feed-forward loop in ovarian cancer cells, that in response to sustained adrenergic signaling, tumor cells secrete BDNF, which then promotes intratumoral innervation via host neurotrophic receptor tyrosine kinase 2 (TrkB) receptors (Allen et al., 2018), denoting that sympathetic pathway might be an upstream inducer of tumor innervation.