This is a pilot study. Subjects with primary soft tissue sarcoma of the extremities may be eligible for this study. Subjects may participate in this study if they are at least 18 years of age. Most participants will be receiving care at the clinical practices of the University of Pennsylvania Health System. Positron emission tomography (PET/CT) imaging will be used to evaluate soft tissue sarcoma hypoxia using an investigational radiotracer, 18F-FMISO. Subjects will also undergo an 18F-FDG PET/CT scan close to the time of their initial hypoxia PET/CT to compare in vivo measures of hypoxia to 18F-FDG uptake. The FDG PET/CT may be performed as part of standard clinical care or as a research scan. Both PET/CT scans will occur prior to starting new therapy.We anticipate enrolling up to 30 subjects who will undergo 18F-FMISO PET/CT, up to 5 of these subjects will participate in a test-retest group that will undergo a second 18F-FMISO scan. Subjects will undergo biopsy as part of their clinical care. Subjects will be asked to consent to allow archived excess tissue to be accessed for the purposes of this study to perform experimental histological assays, if enough tissue is available.

You may be eligible for this study if you meet the following criteria:

• Conditions: TBD
• Age: 99 years or below
• Gender: All