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.) proteinsTwo 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:
Pleomorphic liposarcoma: At least some tumor cells have features of pleomorphic 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 undifferentiated, pleomorphic 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). Treatment and prognosis
The most often used treatment for localized (i.e. no metastases) UPS tumors is complete surgical removal with the object of leaving no tumor cells behind as evidenced by microscopic examinations. Adjuvant therapy combining radiotherapy or/and chemotherapy with surgical resection is employed to reduce the risk of developing recurrent and metastatic disease in cases with high-risk disease (e.g. large tumors, tumors deemed highly aggressive based on their pathology and/or local invasiveness, inoperable tumors, and resections that did not remove all tumor cells).
This inhibition blocks the PD-L1 and PL-L2 ligands located on the surface of normal tissue cells from binding to PD-1 receptors on activated T-cells and thereby blocks the T-cells from organizing an inflammatory response that kills the normal cells. Tumor cells may use this inflammation-evading tactic: they may express PD-L1/PD-L2 and thereby block the T-cell-mediated immune responses to them (see Immune checkpoint). From ~47% to ~73% of UPS cases contain tumor cells that express PD-L1. In a retrospective review of 10 patients with UPS, 1 patient had a complete response, 3 had partial responses, and 6 had no response to pembrolizumab. (Further studies of the 4 pembrolizumab-responsive patients indicated that their tumor cells expressed PD-L1 in two cases but not in the other two cases.) In a retrospective study of 25 patients (21 patients treated with pembrolizumab, 4 treated with other immunotherapy agents), 7 attained stable disease, 7 attained partial responses, and 1 attained a complete response. In a study of 16 patients with UPS, 5 achieved short-term (lasting 1.2 to 1.4 months) stable disease in response to a regimen of pembrolizumab combined with the chemotherapy drug, cyclophosphamide. It is clear that new treatment strategies as well as further studies on the efficacy of pembrolizumab and similarly acting immunotherapy drugs used with or without radiotherapy and/or chemotherapy over longer time periods are needed to evaluate their usefulness in treating UPS. References


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