RecruitingClinical trialNatural History of Medullary Thyroid Cancer to Inform Advanced Disease ManagementThis study utilizes a multi-institutional registry to describe the natural history of medullary thyroid cancer that has spread from where it first started to nearby tissue, lymph nodes, or distant parts of the body (advanced) in understanding disease management. The goal of this study is to learn about how medullary thyroid cancer develops and progresses.