Clinical differences and surgery in follicular vs oncocytic thyroid carcinomas.

Follicular thyroid carcinoma (FTC) and oncocytic thyroid carcinoma (OTC) are distinct entities with differing biological behaviors, yet optimal surgical and radioactive iodine (RAI) therapy management remains debated. Demographic, clinicopathological, and treatment characteristics were gathered from the Surveillance, Epidemiology, and End Results (SEER) database and compared between FTC and OTC according to tumor size. The Kaplan-Meier method and log-rank test were used to analyze cancer-specific survival (CSS). The effect of potential predictors associated with survival was estimated using the Cox regression model. 13,653 patients were included in our study. OTC patients were older and presented higher rates of extrathyroidal extension (ETE) and lymph node metastases (LNM), while FTC had higher distant metastasis (DM) rates. Increasing tumor size was correlated with worse features in both subtypes. Total thyroidectomy (TT) had no CSS benefit over less than TT (LTT) for FTC ≤2 cm or any OTC size group. TT was paradoxically associated with worse CSS for FTC >2 cm. RAI therapy did not improve CSS for patients with ETE (FTC or OTC) or DM (OTC). Multivariable analysis confirmed that TT was independently associated with worse CSS in FTC but not in OTC, while RAI therapy was beneficial in FTC but not in OTC. FTC and OTC exhibited distinct clinical behaviors. In conclusion, TT did not improve CSS for small FTC (≤2 cm) or any OTC, and appeared to be associated with worse outcomes in larger FTC. RAI therapy provided limited benefit in OTC, especially with DM. Treatment should be individualized, avoiding routine aggressive surgery or RAI.