OBJECTIVE Introduction: Approximately 10% of fine needle aspiration biopsy (FNAB) of thyroid nodules may be verified as "suspicious for follicular neoplasm"; this category involves follicular adenoma, follicular carcinoma, follicular variants of papillary carcinoma and subclass "suspicious for Hurthle cell neoplasm". At present, there is no diagnostic tool to discriminate between follicular adenoma and cancer. Most patients are required surgery to exclude malignant process. The aim: To define factors correlating with risk of malignancy in patients with FNAB of thyroid focal lesions and nodules verified as Bethesda tier IV. PATIENTS AND METHODS Materials and Methods: In this study 110 consecutive patients were included. All patients were operated because of FNAB result "suspicious for follicular neoplasm" of thyroid gland at a single institution from January 2016 until March 2020. From this set, six specific categories were defined and the clinical records for patients were collected: sex, age, presence of oxyphilic cells, diameter of the tumour, presence of Hashimoto disease, aggregate amount of clinical and ultrasonographic features of malignancy according to ATA. RESULTS Results: In 18 patients (16,3%) thyroid cancer occurred. Most frequent subtype turned out to be papillary cancer (66,6%). In group of benign lesion (92 patients) predominance of follicular adenoma was disclosed - (49%). Age, gender, tumour diameter, aggregate amount of clinical and ultrasonografic factors, presence of Hashimoto disease and fine needle aspiration biopsy result suspicious for Hurthle cell neoplasm did not correspond to increased risk of malignancy. CONCLUSION Conclusions: In patients with FNAB results classified as Bethesda tier IV there are no reliable clinical features associated with low risk of malignancy and surgery should be consider in every case as most appropriate manner to exclude thyroid cancer .
