To explore the diagnostic value of ultrasound guided fine needle aspiration biopsy (US-FNAB) for thyroid imaging reported and data system (TI-RADS) 4 class ≤10 mm thyroid nodules.

The preoperative ultrasound features of patients with thyroid nodule who received US-FNAB examination were retrospectively analyzed, the malignant risk of each nodule was evaluated and classified according to TI-RADS. TI-RADS 4a class thyroid nodules and diameter ≤10 mm of 365 patients were classified as suspicious nodules and received US-FNAB examination.The nodules were classified as <5 mm and 5-10 mm groups. The results of cytologic diagnosis were compared with the pathological diagnosis, and the differences for nodules with different size were analyzed.

Among 365 TI-RADS 4 class thyroid nodules diagnosed by the cytology, 68 nodules were malignant; 81 nodules were suspicious of malignancy; 193 nodules were benign; 6 nodules were unsatisfactory; and 17 nodules were undetermined.According to postoperative pathology or follow-ups, 153 nodules were malignant and 212 nodules were benign.The difference between US-FNAB results and pathology was not significant (P>0.05). Cytologic positive rate and actually malignant rate of the nodules in 5-10 mm group were higher than <5 mm groups (P<0.05). The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of US-FNAB cytological diagnosis of TI-RADS 4 class thyroid nodule were 92.2%, 96.2%, 94.6%, 94.4% and 94.5%, respectively.

US-FNAB examination is valuable for the diagnosis of TI-RADS 4a class thyroid nodules and improves the preoperative diagnosis.

Thyroid nodule; Biopsy, fine-needle; Ultrasonography; TI-RADS 4a class