Cervical lymph node metastases from thyroid cancer: usefulness of thyroglobulin and calcitonin measurement in fine needle aspirates

Thyroglobulin (Tg) protein measurement in the washout of the needle employed for fine needle aspiration biopsy cytology (FNAB-C) has been report to augment the diagnostic accuracy of FNAB-C in identifying cervical lymph node (CLN) metastasis from differentiated thyroid cancer (TC). We here evaluated the ability of routine measurement of Tg protein (FNAB-Tgp), Tg mRNA (FNAB-Tgm) and calcitonin (CT) mRNA (FNAB-CTm) in the FNAB washout of CLN to improve the accuracy of FNAB-C in the diagnosis of suspicious metastatic CLN. To this end, 35 CLN from 28 patients were evaluated. Histology demonstrated the presence of metastatic papillary TC (PTC) in 26 CLN, metastatic medullary TC (MTC) in 3 CLN, metastatic anaplastic TC (ATC) in 3 CLN and 3 metastatic CLN from extra-thyroidal cancers. The overall accuracy of FNAB-C range from 84.4% to 95.7% when the analysis was restricted to PTC. Both FNAB-Tgp and FNAB-Tgm compared favorably with FNAB-C and shown diagnostic performances not statistically different from that of FNAB-C. However, FNAB-Tgp and FNAB-Tgm/FNAB-CTm were found clinically valuable only in cases in which FNAB-C outcome were inadequate or provided diagnosis inconsistent with patient's clinical parameters. In conclusion, FNAB-C, Tg/CT mRNA and Tg protein determination in the fine-needle washout showed similar accuracy in the diagnosis of metastatic CLN from TC. The obtained results suggest that samples for Tg protein and Tg/CT mRNA measurements from CLN suspicious for metastatic TC should be collected, but their measurements restricted to cases in which FNAB-C provides uninformative or inconsistent diagnosis with respect to patient's biochemical and clinical parameters.