Superior detection of metastatic cystic lymphadenopathy in patients with papillary thyroid cancer by utilization of thyroglobulin washout

Background: Fine-needle aspiration (FNA) cytology has been the standard of care in the workup of cervical lymph nodes (LNs) in patients with recurrent papillary thyroid cancer (PTC) and suspicious cervical LNs. Recently, FNA thyroglobulin (TG) washout measurement has been proposed as an adjunct in the management of these patients. We hypothesize that using FNA-TG washout for suspicious cervical LNs would increase the accuracy of diagnosing metastatic disease especially in cystic and highly vascular cervical LN in patients with recurrent PTC. Methods: This is a retrospective study of a prospectively collected database for patients with thyroid cancer who underwent preoperative FNA followed by selective neck dissection by one surgeon at an academic institution. FNA-cytology and FNA-TG washout were performed simultaneously. A total of 138 patients were included in our study, of which 92 (66.7%) had undergone surgical intervention. Results of both methods were then correlated with the final surgical pathology. Results: FNA-cytology alone showed a sensitivity of 80.0%, specificity of 100.0% with a negative predictive value (NPV) of 60.0%. By contrast, FNA-TG washout had a sensitivity of 95.8%, specificity of 90.5% with a NPV of 86.4%. Combination of the FNA-cytology with FNA-TG washout of cystic/highly vascular LN increased the accuracy of diagnosis with a sensitivity of 98.2%, specificity of 100.00% with a NPV of 95.0%. All 14 malignant cervical LNs with false-negative FNA-cytology showed elevated FNA-TG washout, 10 (71.4%) of which were cystic in nature and 4 were highly vascular on ultrasonography. Conclusion: FNA-TG washout increases the diagnostic accuracy in detecting metastatic disease in patients with recurrent thyroid cancer. FNA-TG washout may be of special diagnostic importance in cystic or highly vascular LNs, which might have falsely negative cytology. Level of Evidence: 2B.