To explore possible lymphatic drainage pathways in the central and lateral neck of patients with papillary thyroid carcinoma (PTC) using a lymphatic tracer.

Totally 52 patients with pathologically node positive (pN+) or clinically node positive (cN+) PTC who underwent central and lateral neck dissection were enrolled in the study. All patients were injected intraoperatively with the lymphatic tracer (nanocarbon suspension injection) and observed developed lymphatic drainage pathways.

Through intraoperative observation, 41 patients developed lymphatic drainage pathways, while 11 patients did not. The development rate was 78.8% (41/52). Twenty-four patients simultaneously developed lymphatic drainage pathways in the central and lateral neck, of which 12 merely developed central lymphatic drainage pathways and 5 merely developed lateral cervical lymphatic drainage pathways. Central lymphatic drainage pathways included a descending lymphatic drainage pathway along lower vessels of thyroid gland, a lateral lymphatic drainage pathway along middle vessels of thyroid gland outwards to the deep neck sheath, and an ascending lymphatic drainage pathway along upper vessels of thyroid gland, and there are multiple anastomotic networks between those pathways. Lateral cervical lymphatic drainage pathways included a lymphatic drainage pathway along lower vessels of thyroid gland to the Ⅳ area of lateral neck through the deep neck sheath, a lymphatic drainage pathway along middle vessels of thyroid gland outwards to the Ⅲ and Ⅳ areas of lateral neck through the deep neck sheath, and a lymphatic drainage pathway which traveled up to the carotid triangle along upper vessels of thyroid gland, reached to the lateral neck through the superficial neck sheath, and then descended along the outer neck sheath.

Several lymphatic drainage pathways can be found in PTC using the lymphatic tracer, and the lymphatic metastasis can be directly transferred to the lateral neck without passing through the central area.