Study of the medial group retropharyngeal node metastasis from nasopharyngeal carcinoma based on 3100 newly diagnosed cases

Summary Purpose Patterns of metastases to the medial retropharyngeal lymph nodes (RPLN) from nasopharyngeal carcinoma (NPC) have gain little attention. Since the incidence of dysphagia was closely related to whether the medial RPLN was irradiated, we carried out a prospective study to explore the patterns of the medial RPLN involvement. Methods and materials Previously untreated NPC patients were required to receive MRI scan. MRI scanning sequences included pre-contrast T1WI, T2WI, and post-contrast T1WI with fat suppression. All images were evaluated by the multi-disciplinary treatment group of NPC. Results 3100 cases of NPC entered this study. 2679 (86.4%) cases had involved lymph nodes. The detailed distribution were: 2341 (87.4%) in level IIb, 1798 (67.1%) in level IIa, 1184 (44.2%) in level III, 350 (14.1%) in level IV, 995 (37.1%) in level V, 115(4.3%) in level Ib, 2012 (75.1%) in the retropharyngeal area. But only 6 (0.2%) were located at the medial group, accompanied with the lateral RPLN and other node metastasis. Only one medial RPLN can be identified in a patient, whereas the number of the lateral RPLNs per affected side varied between one and four. The average size of the medial and lateral RPLNs was 8 ± 4 mm (range, 4–17 mm) and 16 ± 9 mm (range, 5–53 mm), respectively. Conclusions ① Involvement of the retropharyngeal nodes were mainly located at the lateral group, the medial RPLN was rarely seen. ② Metastasis to the medial RPLN was always accompanied with other node metastasis. ③ Only one medial RPLN can be identified in a patient, whereas the enlarged lateral RPLNs per affected side could be multiple. ④ The average size of the medial RPLN was smaller than the lateral RPLNs.