Improving Diagnostic Accuracy of Indeterminate Thyroid Fine-Needle Aspiration Using Results of Ultrasound Examination, Cyclin D1 Immunostaining, and Molecular Testing.

Introduction: Fine-needle aspiration (FNA) is the standard procedure and routine method for diagnosing thyroid nodules. However, indeterminate cytological results diagnoses present considerable challenges in clinical management. This study aimed to evaluate cyclin D1 immunocytochemistry and the Chinese thyroid imaging reporting and data system (C-TIRADS) score, individually and in combination with a simple gene test for cytological diagnosis of Bethesda category III-Ⅴ.

Methods: A consecutive cohort of 177 thyroid FNA specimens with indeterminate diagnosis and available histopathologic follow-up data was collected. The samples were evaluated by cyclin D1 immunocytochemistry and molecular testing for the BRAFV600E mutation or a small panel of markers (BRAF, NRAS, HRAS, KRAS, and TERT). Two experienced sonographers independently reviewed original sonographic images of each nodule and used C-TIRADS to classify the images, obtaining a consensus C-TIRADS score. Identification of the optimal cut-off points of cyclin D1 and C-TIRADS score for the diagnosis of malignancy was evaluated using the receiver operating characteristic (ROC) curves and the assessment of the area under the ROC curve (AUC). The specificity, sensitivity, positive predictive value (PPV) and negative predictive value (NPV) of all tests were evaluated with crosstabs. Logistic regression analysis and ROC curve analysis were used to evaluate the diagnostic accuracy of the three tests individually and in combination.

Results: We enrolled 169 patients (177 thyroid nodules), including 140 malignancies, 15 low-risk neoplasms, and 22 benign lesions. All 177 specimens from the nodules were tested for BRAF V600E, while only 21 specimens adopted the 5-gene detection protocol. With cut-off values set at 10% for cyclin D1 immunocytochemistry and at a C-TIRADS score of 3, along with defining a positive diagnosis as the presence of a mutation in genetic testing, the PPVs for diagnosing thyroid malignancy using the three tests were 97.8%, 90.3%, and 98%, respectively; however, the NPVs were 50%, 24.2%, and 26.3%, respectively. The sensitivities were 87.7%, 83.9%, and 63.9%, and the specificities were 86.4%, 36.4% and 90.9%, respectively. Regarding AUC, cyclin D1 alone demonstrated greater diagnostic accuracy (AUC = 0.921, 95% CI = 0.857-0.985, p = 0.000) compared with the other two methods, which had AUC values of 0.775 (95% CI = 0.703-0.846, p = 0.000) and 0.587 (95% CI = 0.443-0.731, p = 0.235). The combination of two or three tests yielded higher accuracy (AUC = 0.929, 95% CI = 0.873-0.985, p = 0.000; AUC = 0.925, 95% CI = 0.860-0.989, p = 0.000; AUC = 0.937, 95% CI = 0.889-0.985, p = 0.000) compared with cyclin D1 immunocytochemistry alone (AUC = 0.921, 95% CI = 0.857-0.985, p = 0.000).

Conclusion: The addition of cyclin D1 immunocytochemistry or a simple gene panel test, either alone or in combination, significantly improves the limited diagnostic utility of merely repeating the C-TIRADS score in thyroid nodules with indeterminate cytology. Laboratories should integrate these tests to effectively manage uncertain thyroid nodules and reduce diagnostic ambiguity.