Metastasis to lymph nodes at the contralateral entrance point to the recurrent laryngeal nerve in unilateral thyroid papillary carcinoma: a case report and literature review.

Background: Papillary thyroid carcinoma (PTC) is the most common type of thyroid cancer. PTC is slow growing, and prognosis after surgery is excellent. However, PTC is associated with a high incidence of cervical lymph node metastasis, and usually metastasizes from the central lymph nodes to the ipsilateral cervical and mediastinal lymph nodes. Anatomic studies have shown that the thyroid gland and surrounding tissue have an abundant lymphatic network that facilitates tumor dissemination and lymph node metastasis, there may be many ways to connect lymph nodes on both sides of the neck of patients, which needs further research and discussion. Case Description: We report the case of a 45-year-old female who was diagnosed with thyroid cancer of the right lobe and right lateral lymph node metastasis by fine-needle aspiration (FNA). During surgery, 0.2 mL of carbon nanoparticle (CN) suspension was injected into the right lobe of the thyroid gland, which resulted in black staining of a lymph node at the contralateral entrance point to the recurrent laryngeal nerve (LN-epRLN). The black-stained lymph node was resected, and the pathology results revealed lymph node metastasis from thyroid cancer. The left lobe of the thyroid was benign. Conclusions: Retro-tracheal periesophageal lymph node metastasis may be a rare metastatic pathway in thyroid cancer.