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. Overall, metastases have or will develop in up to 40% of individuals with UPS. These metastases are reported to occur in lung (40% to 55% of cases) and less commonly in other sites such as lymph nodes near the primary tumor, brain, pancreas, and heart. Neoplastic Fever A review study conducted in China of 183 individuals with UPS reported that 7 (3.83%) individuals (age 51 to 73 years; median age 62.8 years) had a subtype of the paraneoplastic syndrome termed neoplastic fever, i.e. these individuals suffered continuous, disabling fevers. Their tumors were located within a thigh muscle (4 cases), the upper arm (2 cases), or the lower leg (1 case). Compared to 89 individuals (median age 59.1 years) with a similar distribution of their UPS tumors, individuals with the neoplastic syndrome had similar tumor recurrence rates (57.14% vs 53.93% for the two respective groups) but a lower metastasis rate (14.29% vs 44.94%) and a higher 3-year survival rate (85.71% vs 59.55%). Fever symptoms disappeared in all patients after surgical removal of their tumors. It is suggested that individuals with UPS and neoplastic fever have a more favorable prognosis than individuals with UPS that do not evidence such fevers.
Undifferentiated pleomorphic sarcoma
Low-grade fibromyxoid sarcoma
Solitary fibrous tumor
Sclerosing epithelioid fibrosarcoma
Myxoid liposarcoma
Angiomatoid fibrous histiocytoma
Myxoid tumor
Epithelioid sarcoma