Abstract
BACKGROUND: Although the annual incidence of undifferentiated pleomorphic sarcoma (UPS) is extremely low, it can be subdivided into different subtypes. UPS with fever of unknown origin (also known as neoplastic fever) is a specific subtype of UPS, which shows certain clinical features that differentiate it from other UPS subtypes. However, no studies have focused on this rare UPS subtype. This study retrospectively analyzed the clinical data of patients with UPS to provide a reference for the diagnosis and treatment of UPS with neoplastic fever. METHODS: This study included patients with UPS who were diagnosed and treated between June 2012 and June 2018. We examined whether these patients had a history of neoplastic fever. The characteristics of patients with UPS with neoplastic fever were summarized and analyzed. RESULTS: We reviewed the medical records of 183 patients with UPS. Seven (3.83%) of these patients had neoplastic fever. In patients with UPS with neoplastic fever, the primary lesions were located in the extremities and across the muscle space. In these patients, magnetic resonance imaging showed necrosis within the tumor body and extensive soft tissue edema around the tumor body. Patients with UPS with neoplastic fever had a lower metastasis rate (14.29% vs 44.94%) and a higher 3-year survival rate (85.71% vs 59.55%) than those without neoplastic fever. CONCLUSION: UPS with neoplastic fever is characterized by intratumoral necrosis and extensive edema of the surrounding soft tissues. Patients with UPS with neoplastic fever may have a better prognosis than those without neoplastic fever.