The diagnosis of UPS depends on finding non-specific,<unk>  tumor cells that have features suggestive of UPS and not features of other tumor types that also consist of<unk> ,<unk>  cells. The features primarily involve the expression of certain proteins by the tumor cells. The identifying proteins for UPS tumor cells are given in the preceding section. Identification proteins for tumors that have been confused with UPS inlclude: *<unk>  leimyosarcoma: Desmin and h-caldesmon (i.e. high molecular form of caldesmon.) proteins *<unk>  rhabdomyosarcoma: Desmin and myogenin proteins. * Defifferentiated liposarcoma: MDM2 and CDK4 proteins. * Poorly differentiated carcinoma (i.e. grade 3 or 4 carcinoma): MUC1 (also termed EMA), TP63 (also termed p63; which is detected with the p40 antibody), and various members of the keratin family of proteins. * Melanoma: MLANA (i.e. melanoma antigen recognized by T cells 1 protein), S100, and PMEL (a product of the PMEL gene which is detected using an antibody termed HMB-45.) proteins Two other tumors that may be confused with UPS have microscopic histopathological and/or other features that help make this distinction. These tumors and features are: *<unk>  liposarcoma: At least some tumor cells have features of<unk>  lipoblasts, i.e. variable shaped immature fat cells. * Malignant peripheral nerve sheath tumor: Typically occurs in young children, often develops in a preexisting inoperable plexiform neurofibroma, and often associated with neural tissue. These tumors typically show<unk> ,<unk>  cells that are arranged in whorls, parallel bundles, or rosettes (i.e. circular arrangement resembling leaves in a flowering plant) and often contain large areas of necrosis (i.e. dead or dying cells).
Undifferentiated pleomorphic sarcoma
Low-grade fibromyxoid sarcoma
Solitary fibrous tumor
Sclerosing epithelioid fibrosarcoma
Myxoid liposarcoma
Angiomatoid fibrous histiocytoma
Myxoid tumor
Epithelioid sarcoma