The present study reports findings related to two cases of PAIS with PDGF and VEGF expression following treatment with pazopanib...In a second case with a weak expression of PDGFR-α and -β, the disease progressed rapidly on pazopanib (progression-free survival, 1.1 months)...The level of PDGFR expression in the tumor tissue may therefore be predictive of pazopanib efficacy.