Papillary thyroid carcinoma (PTC) is the most common thyroid cancer and lymph node (LN) metastasis is common in PTC. Lateral LN metastasis is associated with local recurrence of PTC. The aim of this study is to evaluate the patterns of lateral LN metastasis of PTC.

One-hundred seventy four patients who undergone total thyroidectomy, central LN and ipsilatereal or bilateral LN dissection due to PTC 'from 2007 to 2008 in Seoul National University Hospital were retrospectively reviewed. The average age of the patients was 50.4 years and the male to female ratio was 1:4.12. Sixty-seven patients (38.5%) had central LN metastasis and 47 patients (27.0%) had lateral node metastasis.

The factors related with lateral LN metastasis of PTC are male gender, the tumor size, extrathyroidal extension, multifocality and central LN metastasis. The level III LN group was the most frequent site of lateral LN metastasis followed by the jugular, level IV, level II, and level V groups. The jugular LN metastasis is mainly related with the metastasis of the upper lateral neck area, including level II LNs, and the lymphatic pathway to the lower lateral neck area, including level IV, seems to be independent from the jugular LNs. Ten cases had lateral LN metastasis without central LN metastasis (skip metastasis).

Lateral LN metastasis of PTC has a certain pattern. The operator must consider this pattern when managing patients with lateral LN metastasis of PTC.