title: Significance of Incidental Nasopharyngeal Uptake on (18)F-FDG PET/CT: Patterns of Benign/Physiologic Uptake and Differentiation from Malignancy.
abstract: OBJECTIVE
  The purpose of this study was to assess the significance of incidental nasopharyngeal uptake on 18F-FDG PET/CT and to identify image patterns useful in the differentiation between benign or physiologic activity and nasopharyngeal carcinoma.
  
  
  METHODS
  We retrospectively reviewed medical records of patients with nasopharyngeal uptakes on 18F-FDG PET/CT scans taken between January 2010 and July 2011. Patients with head and neck cancer, other metastatic head and neck lesions, or lymphoma were excluded. Total 177 patients were enrolled (Group A). PET images were reviewed for patterns of nasopharyngeal FDG uptake, presence/absence of cervical lymph node uptake and pattern of cervical node uptake. Diagnostic confirmation was made by pathology or clinical and radiological follow-up for 1 year or longer. Furthermore, initial PET/CT images of 48 patients with nasopharyngeal carcinoma (Group B) were reviewed for comparison with PET/CT images of Group A patients.
  
  
  RESULTS
  All nasopharyngeal uptakes in Group A were confirmed to be benign. Group B showed significantly more intense FDG uptake (SUVmax of Group A 3.9 ± 1.4 vs. Group B 10.4 ± 4.6, p<0.001). and asymmetric nasopharyngeal uptake (asymmetric uptake of Group A 67.8% vs. Group B 89.6%). When SUVmax of 6.0 was used as cut off for detection of malignant nasopharyngeal uptake, the area under the ROC curve was 0.93 (95% confidence interval, 0.88-0.98), with a sensitivity of 88.1% and a specificity of 91.7%. Metastatic nodes in Group B showed higher SUVmax (Group A 2.3 ± 0.6 vs. Group B 7.1 ± 4.0, p<0.001) and larger size (short axis of Group A 5.3 ± 2.0 mm vs. Group B 13.1 ± 4.7 mm, p<0.001) than benign nodes of Group A. The majority of Group B cases demonstrated retropharyngeal lymph node uptake (70.8%), compared to only 2 cases in Group A.
  
  
  CONCLUSIONS
  In patients without a history of underlying malignancy involving head and neck, incidental nasopharyngeal uptake on PET/CT does not indicate malignancy. However, if the nasopharyngeal uptake is intense (SUVmax≥6.0) or concomitant retropharyngeal lymph node uptake is present, the possibility of a malignant condition should be considered.
authors.affiliation: Department of Radiology, Seoul St. Mary's Hospital, College of Medicine, The Catholic University of Korea, Seoul, Korea.
authors.forename: Narae
authors.initials: N
authors.lastname: Lee
authors.affiliation: Department of Radiology, Seoul St. Mary's Hospital, College of Medicine, The Catholic University of Korea, Seoul, Korea ; Department of Nuclear Medicine, Seoul St. Mary's Hospital, The Catholic University of Korea, Seochogu Banpodong 505, Seoul, 137-701 Korea.
authors.forename: Ie Ryung
authors.initials: IeR
authors.lastname: Yoo
authors.affiliation: Department of Radiology, Seoul St. Mary's Hospital, College of Medicine, The Catholic University of Korea, Seoul, Korea.
authors.forename: Sonya Youngju
authors.initials: SY
authors.lastname: Park
authors.affiliation: Department of Radiology, Seoul St. Mary's Hospital, College of Medicine, The Catholic University of Korea, Seoul, Korea.
authors.forename: Hyukjin
authors.initials: H
authors.lastname: Yoon
authors.affiliation: Department of Radiology, Seoul St. Mary's Hospital, College of Medicine, The Catholic University of Korea, Seoul, Korea.
authors.forename: Yeongjoo
authors.initials: Y
authors.lastname: Lee
authors.affiliation: Department of Radiology, Incheon St. Mary's Hospital, College of Medicine, The Catholic University of Korea, Seoul, Korea.
authors.forename: Jin Kyoung
authors.initials: JK
authors.lastname: Oh
keywords: FDG; Nasopharyngeal carcinoma; Nasopharynx; PET/CT; Physiologic activity