Nucl Med Mol Imaging.  2015 Mar;49(1):11-18. 10.1007/s13139-014-0299-8.

Significance of Incidental Nasopharyngeal Uptake on 18F-FDG PET/CT: Patterns of Benign/Physiologic Uptake and Differentiation from Malignancy

• Lee N
• Yoo IR
• Park SY
• Yoon H
• Lee Y
• Oh JK

• KMID: 2313240
• DOI: http://doi.org/10.1007/s13139-014-0299-8

Abstract

PURPOSE
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> or =6.0) or concomitant retropharyngeal lymph node uptake is present, the possibility of a malignant condition should be considered.

Keyword

Nasopharynx; FDG; PET/CT; Nasopharyngeal carcinoma; Physiologic activity

MeSH Terms

Axis, Cervical Vertebra
Fluorodeoxyglucose F18*
Follow-Up Studies
Head
Head and Neck Neoplasms
Humans
Lymph Nodes
Lymphoma
Medical Records
Nasopharynx
Neck
Pathology
Positron-Emission Tomography and Computed Tomography*
Retrospective Studies
ROC Curve
Sensitivity and Specificity
Fluorodeoxyglucose F18