Correlation Between the Ultrasonic Size Lesions and the Risk of Central Lymph Node Metastasis in Patients with Papillary Thyroid Microcarcinoma.

ABSTRACT

Objective: This study aimed to analyze the correlation between the ultrasonic measured size (ULMS) and actual pathological measured size (APMS) of papillary thyroid microcarcinoma (PTMC), and to investigate the association of tumor size with metastatic central lymph nodes (CLNM)." Methods: A total of 500 cases with PTMC (APMS) who underwent surgery between August 2009 and May 2016 were reviewed. Paired t test, multivariable logistic regression and ROC curve were used for analyzing the data. The difference and correlation between the APMS and the ULMS were detected by paired t test. The multivariable logistic regression model and Receiver Operating Characteristic curve (ROC) curve area were used to predict the impact of lesion size of PTMC on the risk of CLNM. Results: The overall actual pathological measured value of specimens was smaller than the ultrasonic measured value (among ULMS PTMC, the average value of difference D was -0.775 mm, 95%CI -0.839 mm~ -0.712 mm, P = .000). The ultrasonic tumor size (P = .000, OR=1.129, 95%CI 1.084-1.175) was the risk factor for CLNM. The central lymph node metastasis rate in 500 cases (APMS with ≤ 10 mm) was 37.2%, while 32.6% in 396 cases with ULMS. The CLNM rates of s3 mm-10 mm PTMC single lesions were 20%, 18.18%, 14.89%, 18.18%, 36.73%, 36.36%, 35.29%, and 38.71%, respectively. The metastasis rate of a single lesion≤ 6 mm was significantly lower than that of> 6 mm, which was lower than 20%. The ROC curve indicated that the ULMS was a risk factor for CLNM (optimal threshold of 6.5 mm), 5 or more CLNM (optimal threshold of 6.5 mm), and bilateral CLNM (optimal threshold of 8.5 mm). Conclusion: Ultrasound size is a predictive factor for CLNM in thyroid cancer and that PTMC with a diameter < 6 mm still poses a risk for central metastasis. Prophylactic central dissection is still recommended for PTMC patients, except for those with a single lesion of less than 6 mm in maximum diameter.