F-18 fluorodeoxyglucose chest uptake in lung inflammation and infection

Purpose: F-18 fluorodeoxyglucose (FDG) may accumulate at sites of inflammat ion or infection, making interpretation of whole-body scans difficult in pa tients with cancer. Methods: More than 650 whole-body positron emission tomographic (PET) scans performed to examine patients with cancer were reviewed to identify uptake in pulmonary infection or inflammation based on the appearance of F-18 FDG chest uptake, chest radiographs, computed tomography, or all of these. Results: Ten patients had uptake in benign lung disease. Eight patients had head and neck tumors and two patients had breast cancer. Intense focal or multifocal F-18 FDG chest uptake was seen in 6 of 10 scans. This was diffic ult to distinguish from pulmonary metastases based on the scan appearance. However, in the remaining patients, the uptake was atypical for malignancy and displayed an apical, segmental, or lobar pattern. In all patients, the F-18 FDG lung uptake corresponded to benign radiologic changes (infiltratio n, consolidation, or atelectasis), and the final diagnosis was pulmonary in flammation or infection. Nine patients were asymptomatic and one patient ha d clinical aspiration pneumonia. Follow-up PET scans were performed in five patients to evaluate their conditions. Chest uptake disappeared completely in three patients and partially in two patients, and there were no new fin dings. Variable degrees of F-18 FDG chest uptake have been reported with mo re than 40 different benign causes. They can be classified based on the und erlying mechanism into four major categories: 1) Inflammation or infection, 2) benign tumor, 3) physiologic activity, and 4) iatrogenic. Most of these false-positive cases are included in the first category. Conclusions: Pulmonary infection or inflammation might predispose patients to localized F-18 FDG chest uptake mimicking pulmonary metastases and limit ing the specificity of whole-body scans performed in patients with cancer.