For citation: Vetsheva N.N., Tamazyan T.S., Britvin T.A., Bondarenko E.V. Ultrasound differential diagnosis of follicular thyroid nodules. Head and neck. Russian Journal. 2021;9(4):30–39 (In Russian).
The authors are responsible for the originality of the data presented and the possibility of publishing illustrative material – tables, figures, photographs of patients.

Background: Follicular thyroid nodules or suspected follicular thyroid nodules are classified as Bethesda IV, being found in 10% of fine needle aspiration biopsy samples. Standard ultrasound examination in patients with thyroid follicular neoplasia is insufficient to give a definitive answer about the risk of the nodule malignancy, which affects the treatment tactics. Definitive tumor verification requires a pathological assessment of the macropreparation obtained during surgical treatment.

Purpose: To develop additional ultrasound criteria for the differential diagnosis of follicular thyroid neoplasia. Material and methods: The study included 62 patients who underwent treatment at the Moscow Regional Research and Clinical Institute named after M.F. Vladimirsky from March 1 to November 11, 2020. The patients had Bethesda 4 cytology report result at admission, the mean age was 52,5±13,7 years, the ratio of women to men was 53:9. Based on the set of ultrasound criteria, the nodular formations were classified according to TI-RADS 2020. Additionally, the quantitative characteristics of blood flow in intra-nodular vessels were assessed by spectral Doppler ultrasound. After the surgical treatment and the pathological verification, the ultrasound data obtained before surgery were compared with the morphological data. The analysis of digital data was carried out by methods of variation statistics with the calculation of the mean values, standard deviation, and 95% confidence interval. Sensitivity, specificity, and other criteria were calculated to quantify the performance of the ultrasound criteria in assessing the malignancy risk of thyroid nodules. T-test for independent groups was used when comparing spectral indices in the intra-nodular vessels between the groups of benign and malignant tumors. The results were considered statistically significant at p-value of less than 0.01.

Results: Bethesda 4 nodules were categorized by TI-RADS as follows: TI-RADS 3 – 7 (12%) nodules, of which only 1 (14%) was cancer; TI-RADS 4 – 41 (66%), of which 5 (12%) were malignant; TI-RADS 5 – 14 (23%) nodules, of which 10 were cancers (71%). The diagnostic performance assessment showed low sensitivity values (less than 75%) of all the “major” and “minor” signs of malignancy, with sufficient specificity values (more than 80%). An additional comparison of the spectral characteristics of blood flow in the intra-nodular vessels of the nodules with the pathological examination data was carried out: the mean vascular resistance index was statistically significantly different (p=0,0001) between the intra-nodular arteries of the benign (0,54±0,13) and malignant (0,78±0,17) tumors.

Conclusion: When describing thyroid nodules and categorizing them according to TI-RADS, the “major” and “minor” signs of malignancy need to be considered. An increase in the vascular resistance index in intra-nodular arteries can serve as an additional malignancy criterion.
Key words: ultrasound, thyroid, follicular neoplasia, Doppler, thyroid cancer, TI-RADS, thyroid masses, Bethesda, thyroid nodule

Conflicts of interest. The authors have no conflicts of interest to declare.
Funding. There was no funding for this study.

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