PDGFD and gastrointestinal stromal tumor: PDGFA levels were highest in SyS and lowest in MLPS (P < 4 × 10−9), PDGFB and C levels were lower in GIST (P < 2 × 10−15 and P < 3 × 10−9), while PDGFD expression was similar across histological subtypes (Figure 2).