Utility of Thyroglobulin Measurements in Fine Needle Aspiration Cytology of Lymph Nodes for the Detection of Metastatic Papillary Thyroid Carcinoma
Qing Kay K Li, Summer L Nugent, Joely Straseski, David Cooper, Stefan Riedel, Frederic B Askin, Lori Sokoll. Johns Hopkins Medical Institutions, Baltimore, MD
Background: Ultrasound-guided fine-needle aspiration (US-FNA) cytology is a commonly used method in the surveillance of suspicious lymph nodes (LN) in papillary thyroid carcinoma (PTC). The measurement of thyroglobulin (Tg) levels in LNs during FNA has been suggested to improve the diagnostic yield. We investigated the utility of US-FNA-Tg in the diagnosis of LN suspicious for metastatic PTC.
Design: 227 cases with both US-guided FNA cytology and US-FNA-Tg measurements from our academic center were included. Tg levels were correlated with cytological diagnosis and follow-up surgical resection specimen.
Results: In 41 cases of cytologically diagnosed metastatic PTC, 40 cases were confirmed surgically. The median US-FNA-Tg concentration was 4901.6 ng/ml; whereas, in 124 benign LNs the median Tg concentration was <0.2 ng/ml (P<0.0001). ROC analysis (AUC=0.962 demonstrated a sensitivity of 98% and specificity of 78% at the Tg detection limit (<0.2 ng/mL) (Figure 1), while cutoffs of 9.6 to 100 ng/mL resulted in a sensitivity of 78% and specificity of 98%. Of 15 cases with a cytological diagnosis of “suspicious for PTC”, 9 cases had markedly elevated FNA-Tg. Seven of the 9 cases had follow-up surgeries confirming the diagnosis of PTC. Of 30 cases with a cytological diagnosis of “non-diagnostic”, 8 cases had markedly elevated FNA-Tg with a median of 5,943 ng/ml. Each of 8 cases was confirmed to be metastatic PTC by surgical follow-up.
Conclusions: US-FNA-Tg demonstrates a strong negative predictive value (93%-99%). It may be particularly useful for difficult cases. However, standardization of the sample collection is still needed to further improve the accuracy of the approach.
Tuesday, March 5, 2013 1:00 PM
Poster Session IV # 90, Tuesday Afternoon