Trophoblast Cell-Surface Antigen 2 (Trop-2) Targeted PET/CT in Recurrent and Metastatic Thyroid Cancer

Inclusion Criteria: * Adult patients (aged 18 years or older); * Patients with a history of previously treated thyroid cancer, including DTC and HGFCTC following thyroidectomy with or without 131I therapy, MTC after thyroidectomy, or ATC; either (1) evidence of structural or suspicious lesions on standard of care imaging or (2) biochemical evidence of disease in the absence of structural findings, defined as elevated thyrotropin suppressed thyroglobulin (Tgon ≥1 ng/mL after 131I ablation or ≥5 ng/mL without ablation) with negative anti thyroglobulin antibodies (\<20 IU/mL) for DTC and HGFCTC or elevated calcitonin (\>10 pg/mL) for MTC; * Patients who had scheduled both 68Ga-MY6349 and 68Ga-FAPI PET/CT scans; * Patients who were able to provide informed consent (signed by participant, parent or legal representative) and assent according to the guidelines of the Clinical Research Ethics Committee. * No other anticancer therapy within four weeks prior to PET imaging. Exclusion Criteria: * Pregnant or lactating patients; * Patients with a second primary tumor; * The inability or unwillingness of the research participant, parent, or legal representative to provide written informed consent.