CD274 and undifferentiated pleomorphic sarcoma: However, certain subtypes like alveolar soft-part sarcoma (ASPS), synovial sarcoma (SS), and undifferentiated pleomorphic sarcoma (UPS) display an immunologically “hot” phenotype: higher TMB, elevated PD-L1 expression, and presence of tertiary lymphoid structures (TLS), correlating with improved responses to checkpoint inhibitors (10).