Patterns of retropharyngeal lymph node metastasis in nasopharyngeal carcinoma

This study aimed to investigate the patterns of retropharyngeal lymph node (RLN) metastasis in patients with nasopharyngeal carcinoma (NPC). Sixty-two patients with NPC underwent nasopharyngeal magnetic resonance imaging. Magnetic resonance images were reviewed collectively by the research team. Nodal involvement was classified according to the Radiation Therapy Oncology Group nodal classification guidelines. Locations of the involved RLNs were recorded, and the relationships of RLN metastasis with primary tumor extension and clinical stage were analyzed. Among 62 patients with NPC, 47 (75.8%) exhibited level IIb nodal metastasis, and 39 (62.9%) had RLN metastases. Overall, 60 metastatic RLNs were detected. The center, cranial, and caudal borders of metastatic RLNs respectively included four (6.7%), 17 (28.3%) and three (5.0%) lymph nodes in the occipital bone; 45 (75.0%), 40 (66.7%), and 33 (55.0%) lymph nodes in the first cervical vertebra (C1); 10 (16.7%), three (5.0%), and 21 (35.0%) lymph nodes in the second cervical vertebra (C2); and zero (0.0%), zero (0.0%), and three (5.0%) lymph nodes in the third cervical vertebra (C3). The incidence of RLN involvement did not increase with the incidence of primary tumor invasion to the parapharyngeal space, prevertebral muscle, oropharynx, nasal cavity, skull base, paranasal sinuses, and cavernous sinus. The incidence of nodal metastasis among patients with NPC was highest at the cervical lymph node level IIb, followed by the RLNs. There was a linear decrease in the incidence of metastatic lateral RLNs from levels C1 to C3