Because of their low incidence and frequent grouping with what are now considered to be other sarcoma types, past findings on the clinical behaviour, proper treatment, and prognosis of UPS may be revised with further study.The majority of UPS tumors are highly aggressive, often recur after surgical removal, and often metastasize. They are treated with a combination of surgical resection, radiotherapy, and/or chemotherapy. More recently, UPS tumors have been treated with antibody therapy, i.e. antibodies which in the case of UPS bind to specific antigens on the surface of T-cells (a type of lymphocyte) and thereby promote the ability of these T-cells to organizes an attack on UPS tumor cells. Presentation
UPS commonly presents as a deep-seated, rapidly enlarging, painless mass in individuals aged 50 to 70 years. These masses are rarely superficial lesions and rarely occur in the pediatric population. In a retrospective study of 266 individuals, UPS tumors ranged from 1–55 cm in greatest diameter (average 8.8 cm with 25%, 38%, and 38% having greatest diameters of 0–1, 5–9, and ≥10 cm, respectively). In a study of 205 individuals (median age 59 years) diagnosed with UPS, the tumors were located in the arm or leg (47.3% of cases), abdomen or pelvis (26.8%), thorax (17.6%), and head or neck (8.3%) areas. In rare cases, these tumors have also presented in other sites such as the retroperitoneal space, liver, pleura of the lung, heart, and small intestine. In a retrospective study, distant metastases were detected at the time of initial diagnosis in 6.4% of 266 individuals.
Patients who received surgery alone or surgery plus adjuvant treatment had disease-free survival rates of about 50 and 40%, respectively. A retrospective analysis of  266 patients with UPS were treated with surgery alone (6% of cases), surgery plus radiotherapy (91% of cases), or surgery plus chemotherapy (3% of cases). Post-treatment local recurrences and metastases were observed in 15% and 38% of cases; 5- and 10-year overall survival rates were 60% and 48%, respectively; Overall median survival time were 10.1 years; and patients with tumors ≥10 cm in longest diameter had an almost 6-fold higher rate of developing metastases than patients with tumors 4 cm or smaller. Poorer prognoses were seen in older patients; in patients with tumors that were large-sized, deep-seated, and/or located in a leg; in patients that presented with metastases; and in patients who had positive surgical margins and/or developed local recurrences after surgery. In another retrospective study, 203 individuals with UPS, 141 of whom had metastatic disease, were treated with regimens selected based on the severity of their disease. In this study, the overall 5 year survival rate was 4%. Patients with the most advanced disease had a median overall survival time 11 months. Immunotherapy
Recent studies have treated UPS by targeting the immune system with pembrolizumab. Pembrolizumab is a manufactured IG4 therapeutic monoclonal antibody that binds to and inhibits stimulation of the PD-1 receptors expressed on the surface of activated T-cells.