PSMB9 and mesenchymal cell neoplasm: A differential diagnostic method with IHC staining using a combination of several monoclonal antibodies against LMP2/β1i and other candidate cellular factors, such as caveolin 1, cyclin B, cyclin E, Ki-67/MIB1, and CD44, has been investigated for uterine mesenchymal tumors, including uLMS (Table 1) [18,19].