Magnetic resonance imaging of retropharyngeal lymph node metastasis in nasopharyngeal carcinoma: Patterns of spread

Purpose: To investigate the incidence, distribution, and spread pattern of retropharyngeal lymph node (RLN) involvement in patients with nasopharyngeal carcinoma (NPC) by using magnetic resonance imaging (MRI). Methods and Materials: The MR images of 275 patients with newly diagnosed NPC were reviewed retrospectively. Nodes were classified as metastatic based on size criteria, the presence of nodal necrosis, and extracapsular spread. Results: Retropharyngeal lymph node involvement was detected in 175 (63.6%) patients. Metastatic RLNs were seen at the following levels: occipital bone, 24 (9.6%) nodes; C1, 157 (62.5%) nodes; C1/2, 40 (15.9%) nodes; C2, 27 (10.8%) nodes; C2/3, 1 (0.4%) node; and C3, 2 (0.8%) nodes. The incidence of RLN involvement was equal to the incidence of cervical lymph node involvement (81.4% vs. 81.4%) in 215 patients with nodal metastases. A significantly higher incidence of metastatic RLNs was observed in the presence of oropharynx, prestyloid parapharyngeal space, post-styloid parapharyngeal space, longus colli muscle, medial pterygoid muscle, levator muscle of velum palatini, tensor muscle of velum palatini, Level 11 node, Level III node, and Level V node involvement. A significantly lower incidence of metastatic RLNs was found in T1, NO, and Stage I disease. Conversely, no significant difference in the incidence of metastatic RLNs was observed between TI, 2, and, 3; N2 and N3; or Stage 11, 111, and IV disease. Conclusions: There is an orderly decrease in the incidence of metastatic lateral RLNs from the C1 to C3 level. Metastatic-RLNs associate well with involvement of certain structures in early stage primary tumors and lymph node metastases of the upper jugular chain (Level II, Level III nodes) and the posterior triangle (Level V nodes). Both RLNs and cervical Level 11 nodes appear to be the first-echelon nodes in NPC. (c) 2006 Elsevier Inc.