False-positive finding of retropharyngeal lymph node recurrence in both fluorine (18)FDG PET and MRI in a patient with nasopharyngeal carcinoma.

BACKGROUND Biopsy of the retropharyngeal node is not routinely accessible. The diagnosis of retropharyngeal lymph node recurrence in patients with nasopharyngeal carcinoma (NPC) is often based on an imaging study. METHODS We reported a patient with NPC who was incorrectly diagnosed with left retropharyngeal lymph node recurrence by both MRI and positron emission tomography (PET)/CT. RESULTS A woman who was treated for stage IVA NPC 2 years previously was found to have a nodal lesion in the left retropharyngeal space on MRI together with focal fluorodeoxyglucose (FDG) uptake on PET/CT. Locoregional recurrence was suspected, and surgery was performed. Subsequent pathology results showed reactive lymphoid hyperplasia. CONCLUSION Although tissue biopsy for the retropharyngeal node is technically difficult, this case demonstrates that tumor recurrence cannot be diagnosed even based on both positive findings on MRI and PET/CT in patients with NPC.