Extra-thyroidal malignancy history and postoperative malignancy in Bethesda category III thyroid nodules

Aims: Management of Bethesda category III (atypia of undetermined significance/follicular lesion of undetermined significance, AUS/FLUS) thyroid nodules remains challenging due to their heterogeneous malignancy risk. Patients with a history of extrathyroidal malignancy represent a clinically distinct subgroup, yet data regarding malignancy outcomes in this population are limited.Methods: This retrospective study included 336 patients who underwent thyroid surgery between 2013 and 2023 with preoperative Bethesda category III cytology. Among them, 23 patients (6.7%) had a documented history of extra-thyroidal primary malignancy. Demographic characteristics, thyroid functional status, laboratory parameters, ultrasonographic findings, and history of extra-thyroidal malignancy were recorded. Suspicious ultrasound features were evaluated. Postoperative histopathology was used as the reference standard. Results: Overall, malignant pathology was identified in 101 patients (30.1%), while 235 patients (69.9%) had benign pathology. A history of extra-thyroidal malignancy was significantly more frequent in patients with malignant postoperative pathology compared with benign cases (10.0% vs 5.5%, p=0.008). Malignant cases were younger than benign cases (p