18F-PSMA (n=3)  Inclusion criteria:  Men >18 yo with suspected prostate cancer metastasis who are candidates for initial definitive therapy or with suspected recurrence based on elevated serum PSA level  Prior imaging study (CT, and/or MRI and/or Bone scan and/or Fluciclovine scan) suspicious for metastatic disease, obtained not earlier than 4 months from the research scan date.  68Ga DOTATATE (n=3)  Inclusion Criteria:  Persons > 18 yo suspicious for or diagnosed with somatostatin receptor positive neuroendocrine tumors (NETs) Prior DOTATATE PET/CT scan suspicious for tumor obtained not earlier than 4 months from the research scan date.  Exclusion Criteria:  Recent administration of long-acting somatostatin analogs  18F-FES (n=3):  Persons > 18 yo with recurrent or metastatic breast cancer Prior imaging study (CT, and/or US, and/or MRI, and/or bone scan and/or FDG PET/CT) suspicious for tumor, obtained not earlier than 4 months from the research scan date. Biopsy proven ER-positive breast cancer (any location) in the past 6 months  Exclusion Criteria:  • History of ER modulators and ER down-regulators such as tamoxifen and fulvestrant in the past 8 and 28 weeks, respectively  Exclusion Criteria for all participants:  Adults unable to consent Pregnant/lactating persons Prisoners Unable to lie supine for up to 90 minutes at different timepoints in the PET scanner Uncontrolled claustrophobia Any significant medical condition that in the opinion of the investigator would prevent the subject from participating and/or adhering to study related procedures or interfere with subject safety