Dedifferentiation and Redifferentiation of Follicular-Cell-Derived Thyroid Carcinoma: Mechanisms and Therapeutic Implications

Follicular-cell-derived thyroid carcinoma, while typically associated with a favorable prognosis, can undergo dedifferentiation into poorly differentiated (PDTC) or anaplastic thyroid carcinoma (ATC), leading to enhanced aggressiveness and radioiodine resistance. This review systematically examines the genetic and molecular mechanisms driving this pathological progression, highlighting the roles of key mutations-such as BRAF, RAS, TERT, and TP53-and the disregulation of signaling pathways, including MAPK and PI3K/AKT. These alterations promote the loss of thyroid-specific functions, including iodide metabolism, and correlate with poor clinical outcomes. In recent years, therapeutic strategies aimed at tumor redifferentiation have emerged as a promising approach for radioiodine-refractory disease. We summarize recent advances in the use of targeted agents, particularly BRAF and MEK inhibitors, to restore radioiodine avidity and improve treatment response. While early clinical studies show encouraging results, including tumor shrinkage and restored RAI uptake in selected patients, challenges such as treatment resistance and patient selection remain. Future efforts should focus on refining molecular stratification, developing rational combination therapies, and integrating novel modalities such as immunotherapy to overcome resistance. A deeper understanding of redifferentiation mechanisms not only provides insights into thyroid cancer progression but also supports the development of personalized treatment strategies for high-risk patients.