Differentiating the location of cervical lymph node metastasis is very useful for estimating the risk of distant metastases in papillary thyroid carcinoma.

Objective A larger primary tumour size, greater numbers of cervical lymph node ( LN) metastasis are associated with a higher risk of distant metastases in papillary thyroid carcinoma ( PTC). However, the impact of the location of cervical LN metastasis on distant metastasis is controversial. The aim of this study was to evaluate the risk of distant metastases according to the tumour size and LN status in PTC patients, with special consideration of the LN metastasis pattern. Patients This retrospective cohort study reviewed 1700 classical PTC patients who underwent initial thyroid surgery at Asan Medical Center between 2000 and 2004. Results The cumulative risk of distant metastases was increased with the increase in tumour size and was significantly different according to the location of involved LNs by the tumour node metastasis (TNM) staging. The cumulative risk in pN1b group showed the steepest increasing pattern with the increase in tumour size compared with pN1a and pN0/Nx group. When we analysed the cumulative risk of distant metastases according to the number of involved LNs, patients with more than 20 involved LNs also had the steepest increase in the risk of distant metastases with the increase in tumour size. However, only the location of involved LNs, not the number of involved LNs, was associated with distant metastases in multivariate analysis. Conclusions We confirm that the location of involved LNs categories based on the TNM staging system is more useful than the number of involved LNs categories for estimating the risk of distant metastasis in PTC. Differentiating N1a disease from N1b disease is important for the follow-up and management of patients with PTC. [ABSTRACT FROM AUTHOR]