Endonasopharyngeal ultrasound and magnetic resonance imaging features of recurrent retropharyngeal nodes in nasopharyngeal carcinoma patients: A radiologic-histopathologic study.

BACKGROUND:The imaging criteria of malignant retropharyngeal lymph node (RLN) in nasopharyngeal cancer (NPC) have yet to be fully elucidated. This study aimed to establish predictive models based on ultrasound (US) and magnetic resonance (MR) characteristics for identifying malignant RLN in NPC patients after radiotherapy. METHODS:81 post-radiotherapy NPC patients with abnormal enlargement of RLN underwent endonasopharyngeal ultrasound-guided fine-needle aspirations (EPUS-FNA) to access the nature of RLN. The following features were assessed on US and MR: size, margin, vascular signal, echogenicity, enhancement signal and accompany with suspicious cervical nodes or not. A multivariate analysis was performed to screen out high-risk imaging features for recurrent RLN (RRLN), and models for the diagnosis of RRLN was constructed and tested with internal verification. We evaluated the clinical usefulness of the models through comparison of C-index and decision curve analysis. RESULTS:High-risk features of RRLN were heterogeneous echo (p < 0.01), vascular signal (p < 0.01) on EPUS, heterogeneous enhancement (p < 0.01) and minimum axis diameter > 10 mm (p < 0.01) on MR. The models based on the US and MR features showed good discrimination (AUC of 0.76 in the US model, 0.74 in the MR model and 0.77 in the US + MR model) and good net benefit in the validation group. CONCLUSION:Prediction models based on the US and MR features show good diagnostic performance for RRLN after radiotherapy in NPC patients. The combination of EPUS and MR may be constructed to provide prompt and reliable guidance to manage RLN.