Endocrine Abstracts

Introduction: Thyroid nodules represent a common cause of specialist consultation, with a risk of malignancy of 4-15%. The most widely used cytopathological method for diagnosing thyroid cancer is fine-needle aspiration biopsy (FNAB) of thyroid nodules and the use of the Bethesda system (BS) for cytopathological reporting. We conducted the present study to report our experience using the BS, and to compare the results obtained with this system with the final histopathological results of the thyroidectomies performed.

Material and methods: Analytical study was carried out comparing the results of FNAB according to the BS, and the final result of histopathology of patients with thyroid gland lesions who consulted at the Hospital Central de la Defensa Gómez Ulla (Madrid), during the year 2020. The results were expressed as mean ± standard deviation for quantitative variables and as absolute and relative frequency for qualitative variables. The comparison between the characteristics of the sample and the BS was carried out using the chi-square test and ANOVA, adjusting for the Bonferroni host-post test. Statistical software: Stata InterCooled for Windows version 16. Significance level: 0.05.

Results: Reports of 201 cytologies corresponding to 152 patients were reviewed. Mean age 65.6 ± 15.1 years. Predominantly female sex 75.0%. Main reason for FNAB request: size of the nodule (40.5%). Mean size of biopsied thyroid nodules: 23.5±10.5 mm. The highest percentage of cytologies corresponded to the Bethesda II category: 152 (75.6%), followed by Bethesda I: 26 (12.9%), III: 11 (5.5%), V: 6 (3, 0%) and IV: 3 (1.5%), VI: 3 (1.5%). 15 patients (9.9%) underwent surgery, corresponding to 25 cytologies performed (12.4%). 7 malignancies were identified. There was a final histopathological result of malignancy in 14.3% of Bethesda II, 33.3% in Bethesda III, 0% in Bethesda IV, 100% in Bethesda V, and 66.7% in Bethesda VI (P-value = 0.013). Overall, categories IV, V and VI had a malignant lesion in the final histopathology diagnosis in 66.7% of cases (positive predictive value, PPV). 85.7% of Bethesda II, had a benign lesion (negative predictive value, NPV). Considering only patients with satisfactory samples, the diagnostic accuracy was 73.7%.

Conclusion: The BS for the interpretation of the FNAB of thyroid nodules enhances the diagnostic certainty and assists the medical-surgical team in the therapeutic decision. In our institution, most part of cytologies were reported as benign. Regarding patients who underwent thyroidectomy, FNAB showed a high NPV, with a lower PPV.