Diagnostic utility of thyroglobulin detection in fine-needle aspiration of cervical cystic metastatic lymph nodes from papillary thyroid cancer with negative cytology

Cystic changes in metastatic cervical lymph nodes (CLN) from papillary thyroid cancer (PTC) may be a diagnostic pitfall in fine-needle aspiration biopsy (FNAB) cytology. We investigated in a series of CLN metastases from thyroid cancers (TC), including cystic PTC, and from a wide spectrum of extrathyroidal malignancies, the diagnostic role for metastatic TC of the rapid detection of thyroglobulin in eluates from FNAB (FNAB-Tg) of CLN. The study was carried out in a group of 79 subjects (22/57 M/F; median age, 56 years; range, 20-86 years) with enlarged CLN and thyroid nodules (TN), examined for potential metastatic TC, and harboring a large spectrum of incidentally diagnosed extrathyroidal malignancies (n = 24, mostly represented by lymphomas, lung, and breast cancers), CLN metastases from thyroid cancers (n = 28, including 6 cystic metastatic PTC), 6 specific lymphadenitis and 21 reactive lymphadenitis mostly detected (n = 16) during follow-up of patients with previously ablated TC. Markedly high FNAB thyroglobulin (Tg) values were found in all metastatic CLN TC. Two of the six cases with cystic metastatic CLN PTC were diagnosed by FNAB-Tg but not by cytology. In conclusion, FNAB-Tg has been confirmed as an easy modality and fast procedure to diagnose CLN metastasis from TC and high FNAB-Tg values with nondiagnostic cystic cytology strongly suggest cystic metastatic PTC.