PDGFRB and neoplasm: Given that both siblings and NSTS-47 cells harbor the c.1681C>T (p.R561C) mutation in PDGFRB and that PDGFR-beta c.1681C>T (p.R561C) mutants are constitutively phosphorylated and can activate various signaling pathways [21], we assessed the phosphorylation level of 49 RTKs and 26 other signaling proteins in tumor samples as well as in NSTS-47 cells.