SIRPA and synovial sarcoma: SIRPα+ macrophages were identified in 31.3% of total cases; the subtypes of STS most infiltrated by SIRPα+ macrophages are dedifferentiated liposarcoma (77% of cases), angiosarcoma (75%), and well-differentiated liposarcoma (65%), whereas the subtypes less infiltrated by SIRPα+ macrophages are fibromyxoid sarcoma (0% of cases), epithelioid sarcoma (13%), and synovial sarcoma (14%).