Primary treatment strategies for ATC have included surgical resection combined with radiotherapy, chemotherapy, or concurrent chemoradiation therapy. Despite these aggressive approaches, disease recurrence or progression remains frequently observed. Recent advances in molecular diagnostics and targeted therapy development have expanded treatment options for ATC patients with actionable genetic alterations, such as BRAF mutations or NTRK fusions. Nevertheless, for patients lacking identifiable targetable mutations, therapeutic options remain limited and clinical outcomes are poor. To address this unmet clinical need, the investigators aim to analyze baseline characteristics, treatment outcomes, and biomarker profiles from a larger cohort of ATC patients, with the goal of identification of predictive biomarkers and potential therapeutic targets. Given the rarity of ATC, conducting comprehensive studies at a single institution is challenging. Therefore, the investigators propose to establish a multi-center registry to systematically collect clinical data and tumor specimens from ATC patients.