• INCLUSION CRITERIA:
• Histologically confirmed pancreatic ductal adenocarcinoma (PDAC), cholangiocarcinoma, hepatocellular carcinoma (HCC), gastric cancer, bladder cancer, ovarian cancer, pheochromocytoma/paraganglioma (PPGL), small cell lung cancer (SCLC) or extrapulmonary neuroendocrine cancer (EP-NEC), mesothelioma or sarcoma.
• Participants must be scheduled or intended to receive treatment for their cancer.
• Evaluable disease
• >= 18 years old.
• Eastern Cooperative Oncology Group (ECOG) performance score <= 2.
• Individuals of child-bearing potential (IOCBP) and individuals that can father children must agree to use effective contraception (barrier, hormonal, intrauterine device (IUD), surgical sterilization, abstinence) at the study entry and for 2 months after each (18F) FAPI-74 imaging. Sperm may not be frozen or donated within the same period.
• Must be willing to discontinue breastfeeding for 2 months after each study imaging.
• The ability of participant to understand and the willingness to sign a written informed consent document.

EXCLUSION CRITERIA:

• History of allergic reactions attributed to compounds of similar chemical or biologic composition to [18F]FAPI-74 or other agents used in the study.
• History of severe claustrophobia unresponsive to oral anxiolytics or history of any other condition preventing the ability to lie on the imaging scanner for up to 45 minutes.
• Weight > 350 lbs., or inability to fit within the imaging gantry.
• Positive Beta-human chorionic gonadotropin (Beta-HCG) serum or urine pregnancy test performed in IOCBP at screening.
• Uncontrolled intercurrent illness, or medical condition(s) including but not limited to renal failure, liver failure, or psychiatric illness/social situations evaluated by medical history and physical exam that would limit compliance with study requirements and potentially increase risk for the participant.
• Serum creatinine > 2 times the upper limit of normal.
• Liver transaminases (ALT, AST) greater than 3 times the upper limit of normal.