F-18 FDG PET scan findings in patients with Loeffler's syndrome

: This study aimed to evaluate the F-2-fluoro-2-deoxyglucose positron emission tomography (F-18 FDG PET) findings of Loeffler's syndrome and to determine differential features between lung malignancy and Loeffler's syndrome.

: F-18 FDG PET and low-dose chest CT scans were performed to screen for lung cancer. Eleven patients who showed pulmonary lesions on CT scan with peripheral blood eosinophilia were included. PET scans were evaluated by mean and maximum standardized uptake values (SUVs) of abnormalities. CT findings were reviewed and correlated with the PET findings. In all patients, follow-up CT scans and PET scans were done from 1 to 4 weeks after the initial study.

: F-18 FDG PET scans identified metabolically active lesions in 9 of 11 patients. Maximum SUVs ranged from 2.8 to 10.6, and mean SUVs ranged from 2.2 to 7.2. The other 2 patients had maximum SUVs of 1.3 and 2.2. Follow-up PET scans showed a decreased degree of initially noted FDG uptakes or migration of the lesion. The CT scan showed nodular lesions with a peripheral halo (n = 6), ground-glass attenuation (n = 4), and consolidation (n = 1). Follow-up CT scans revealed decreased size and extent of the initial lesions in 7 patients and migration in 2 patients. The other 2, who had relatively mild F-18 FDG uptakes, showed complete radiographic resolution of the lesions.

: A single F-18 FDG PET study is not useful in differentiating benign and malignancy in patients with Loeffler's syndrome. Correlation and follow-up of PET and CT scan for the identification of abnormalities and their changes can be helpful for the differentiation between lung malignancy and Loeffler's syndrome.