KDR and neoplasm with perivascular epithelioid cell differentiation: The therapeutic efficacy of single-agent angiogenesis inhibitors for advanced PEcoma is often limited, and the therapeutic strategy of VEGFR inhibitors combined with mTOR inhibitors exerts a synergistic effect, blocking the survival and proliferation signals of tumor cells from different angles and reducing the possibility of tumor cells to develop drug resistance through activation of other bypass signaling pathways, thus delaying the emergence of drug resistance (24).