Evaluation of 19 cases of benign lesions with high accumulation of tracer on ~(18)F-FDG PET imaging

Objective To review PET images of benign lesions with high accumulation of 18F-FDG and to analyse the possibility of FDG PET imaging for differentiating the benign from the malignant. Methods 18F-FDG PET imaging was performed on 19 patients with benign diseases including 13 cases of active tuberculosis and 6 cases of other benign diseases. Positive pathologic or bacteriological results were obtained for all the patients. PET images were evaluated with standardized uptake value (SUV), lesion shapes, and radioactivity distribution. CT or MRI and histopathologic findings also were reviewed. Results ①Thirteen patients with active tuberculosis showed high uptake of 18F-FDG. The SUV was 3.1±1.8. But radioactivity distribution in some lesions was not uniform and there were defect areas in the lesions. Histopathologic findings proved that the defect areas were induced by caseous necrosis. Seven cases of pulmonary tuberculosis showed two or multiple stripe and funicular high accumulation and other lesions displayed high uptake in sheet or irregular shape; 1 case of scrofula and 1 case of splenetic tuberculosis showed defect areas in the lesions; the other scrofula case showed focal intense uptake. Two of lumbar tuberculosis showed intense uptake in the lumbar vertibra, and one of the two cases complicated with the cold abscess showed bilateral high accumulation in the shape of sheet along musculus psoas major. In the peritoneal tuberculosis case, PET images showed diffuse incrassation and intense uptake in peritoneum and mesentery. CT findings revealed that the peritoneum and mesentery thickened. ②Pulmonary abscess,pulmonary cryptococcus granuloma, cerebral cryptococcus granuloma, pulmonary inflammatory pseudotumor, leiomyoma, and breast adenoma all showed high accumulation in the shapes of nodule or mass. Mean SUV was 4.5±3.1. CT or MRI findings were the same as on PET images shape. Histopathologic work-up did not find necrosis in the lesions. Conclusions Some benign lesions commonly cause an increase in 18F-FDG uptake. It is helpful for diagnosis of tuberculosis by analysing the shapes and radioactivity distribution of the lesions on the images. Most of positive 18F-FDG PET results were not quite determinative for differentiating the benign from the malignant.