INCLUSION CRITERIA:  Patients with HTC, DTC, and MTC will be identified by the investigators. The potential candidates for the study will be screened for eligibility to participate in the study and invited to sign the Research 68Gallium-DOTATATE PET/CT imaging informed consent form  In order to be eligible to participate in this study, an individual with DTC (including HTC) must meet all of the following criteria:  Male or female, aged >=18 years.  Patients with established thyroid cancer diagnosis presenting with either:  Locally advanced or distant metastases, which are RAI-non-avid based on the or diagnostic or post-treatment whole body scan (WBS) OR Patients with RAI-non-responsive disease, who have the evidence of disease progression defined by RECIST criteria after therapy with RAI.  In order to be eligible to participate in this study, an individual with MTC must meet all of the following criteria:  Male or female, aged >=18 years. Patients with locally advanced or metastatic MTC or patients suspected of locally advanced or metastatic MTC with calcitonin level > 500 pg/mL.  EXCLUSION CRITERIA:  Subjects with either HTC, DTC, or MTC who meet any of the following criteria will be excluded from participation in this study:  Pregnancy or lactation Serious underlying medical conditions that restrict diagnostic testing or therapy such as renal failure, congestive cardiac failure or active coexisting non-thyroid carcinoma; Patients unable to give informed consent.