Benign foci in the mediastinum or hilum in non-small cell lung cancer: Description on 18F-FDG PET/CT

Objectives Focal FDG uptake in the mediastinum or hilum turn out to be benign is not an unusual PET/CT finding in the tuberculosis-endemic country. The aim of this study is to describe the PET/CT findings of the mediastinal or hilar FDG foci associated with benign etiology in non-small cell lung cancer (NSCLC).

Methods Forty-eight consecutive patients with NSCLC showing benign mediastinal or hilar foci on 18F-FDG PET/CT were enrolled retrospectively (35 males, 13 females; age 70.5+-6.9 years). The gold standard was histologic diagnosis or clinical follow-up over 8 months (range 8-22 months, mean 15.3 months). A maximal SUV (maxSUV) was measured at a FDG focus with the most intense uptake of the mediasinal and hilar foci in a patient. Follow-up PET/CT was performed in 16 patients.

Results The findings of benign foci were classified into 5 groups according to the hilar distribution and the presence of calcification; 1) Bilateral hila foci with calcification (16 scans (33.3%), maxSUV 5.3 +- 1.93, 15 mediastinal involvement (MI)), 2) Bilateral hilar/mediastinal foci without calcification (14 scans (29.2%), maxSUV 4.4 +- 1.2, 6 MI), 3) unilateral hilar/mediastinal foci with calcification (5 scans (10.4%), maxSUV 3.6 +- 1.0, 2 MI), 4) unilateral hilar/mediastinal foci without calcification (10 scans (20.8%), maxSUV 4.7 +- 3.0, 3 MI) and 5) mediastinal foci only (3 scans (6.3%), maxSUV 2.9 +- 5.0). Of the 16 follow-up scans, less than 2 unit increase or decrease in SUV was seen in 10 scans and no remarkable change in size of lymph nodes was seen in 14 scans.

Conclusions Cautious consideration of these findings is required for accurate interpretation of PET/CT scans to avoid an unnecessary invasive procedure in NSCLC