PDGFRB and neoplasm: These features are believed to reflect the inhibitory effects of sunitinib on vascular endothelial cell VEGFR expression and on tumor pericyte PDGFR expression, resulting in disrupted, congested, tortuous, and leaking tumor vessels associated with necrotic areas in the tumor, rather than significant shrinkage of tumor cells [18], which may indicate that a reduction in tumor density is a more sensitive parameter than tumor size in evaluating the early responses to sunitinib treatment.