The diagnostic role of FNA based on clinicopathological features in thyroid malignancy

Thyroid nodules are mostly benign lesions within the thyroid, with a small percentage being malignant. The decision for surgery is mainly based on the fine needle aspiration (FNA) cytology report, which is categorized into six categories from non-diagnostic to malignant. The accuracy of FNA is of utmost importance to minimize the complications due to misdiagnosis.

In a retrospective study, we analyzed 310 patients who underwent thyroidectomy due to suspicious thyroid nodules with both FNA and histopathological results. We reviewed patient files, extracting demographic data, FNA results, and final histopathology reports and grouped them based on the size of the nodules. Sensitivity, specificity, and predictive values were calculated.

The average age of the patients was 42.9 ± 13.2 years, and the average size of the largest nodule diameter was 2.1 ± 1.89 cm. Histopathological evaluation of specimens obtained during surgery showed that 184 (59.4%) samples were malignant and 126 (40.6%) were non-malignant. The overall specificity was 96.8%, and the sensitivity was 89.6%, and the accuracy of FNA in diagnosing malignancy was 92.2%. Logistic regression analysis revealed that Bethesda classification (OR: 2.34; 95%CI: 1.73-3.16; P < 0.001), and also tumor size (OR: 2.02; 95%CI: 1.32-3.10; P = 0.001) exhibited a significant direct correlation with the capability of FNA in accurately diagnosing malignancy. The highest FNA accuracy of malignancy detection was among nodules above 3 cm (97.1%) while in nodules smaller than 1 cm the accuracy was 73.2%.

FNA is a suitable diagnostic tool for detecting malignant nodules, while diagnostic capability varies with approaches to indeterminate FNA results. False positive and negative rates are crucial, with challenges in diagnosing malignancy in the context of multinodular goiter cases and smaller nodules.