Thyroid cancer detection rate and associated risk factors in patients with thyroid nodules classified as Bethesda category III

Abstract

Introduction: Ultrasound guided fine-needle aspiration (FNA) is a standard procedure for thyroid nodules management and selecting patients for surgical treatment. Atypia of Undetermined Significance (AUS) or Follicular Lesion of Undetermined Significance (FLUS), as stated by The Bethesda System for Reporting Thyroid Cytopathology, is a diagnostic category with an implied malignancy risk of 5-15%.

Materials and methods: In our study we reviewed the cytology and histopathology reports, as well as clinical and ultrasound data, from 112 AUS/FLUS thyroid nodules in 105 patients, in order to evaluate the malignancy rate and to assess factors associated with malignant outcome.

Results and discussion: Of the total 112, 85 nodules (75.9%) were referred to surgery, 21 (18.8%) were followed-up by repeat FNA and 6 (5.3%) were clinically observed. Final diagnosis of malignancy had 35 cases (31.2%) and 77 (68.8%) had benign lesions. The most frequent type of cancer was Papillary Thyroid Carcinoma (PTC) - 58.1% PTC and 25.8% follicular variant of PTC. The final diagnostic outcome - benign or malignant, was compared to clinical data and ultrasonographic features. Patients’ younger age, smaller nodule size, hypoechoic nodule and presence of calcifications were shown to be statistically significant risk factors for malignancy. Therefore, since the rate for malignancy in our study was higher than estimated by the Bethesda System, clinical and ultrasound factors should be taken in consideration when decision for patient treatment is being made.