Preoperative USG and CT Scanning for Predicting Regional LN Metastasis of Papillary Thyroid Carcinoma

Lim, Young Ah; Kang, Kyung Ho; Kim, Byung Seup; Kim, Lee Su

Abstract

PURPOSE
Lymph node (LN) metastasis of papillary thyroid carcinoma (PTC) is related to a high local recurrence rate and a low disease-specific survival rate. So, the diagnosis of LN metastasis according to the compartment is important for surgical planning. We evaluated the value of preoperative USG and CT for predicting LN metastasis
METHODS
USG, CT or both were performed preoperatively for 325 consecutive patients who were newly diagnosed with PTC and who were operated on between Dec 1, 2004 and Dec 31, 2008. The reports of the preoperative USG and CT were compared with the histopathologic results. The accuracy of these studies for assessing LN metastasis were calculated, and we investigated whether combined USG and CT (US/CT) showed any additional benefit over USG or CT only.
RESULTS
For the central compartment, USG, CT and US/CT showed high specificities (98.2%, 98.6%, 98.2%, respectively) and low sensitivities (7.1%, 4.6%, 12.0%, respectively), and US/CT showed higher sensitivity than CT only. For the lateral compartment, USG demonstrated higher sensitivity and lower specificity compared with CT (76.2% vs 43.5%, 50.0% vs 70.0%, respectively), and US/CT had a higher sensitivity than CT only (81.0% vs 43.5%, respectively). By the per patient analysis, the sensitivity of US/CT (38.6%) was higher than those of USG (30.6%) or CT (19.3%),and the specificity was highest for CT (96.4%).
CONCLUSION
Prophylactic central LN dissection for PTC can be justifiedby the low sensitivity and high specificity of USG and CT for predicting central LN metastasis. For the lateral LN compartment, a combination of USG and CT can increase the sensitivity for predicting LN metastasis.