FALSE-POSITIVE 2-[F-18]-FLUORO-2-DEOXY-D-GLUCOSE POSITRON-EMISSION-TOMOGRAPHY STUDIES FOR EVALUATION OF FOCAL PULMONARY ABNORMALITIES

Positron emission tomography (PET) with 2-[F-18]-fluoro-2-deoxy-D-gluc ose (FDG) call demonstrate the glucose metabolism characteristics of a lesion, which may be helpful in differentiating between benign and ma lignant focal pulmonary lesions. Malignant cells demonstrate higher gl ucose metabolic activity than benign lesions. However, some inflammato ry processes also show significant FDG uptake. We present two cases wh ere high FDG uptake was found in inflammatory lesions in the lungs. Th e first case was that of a 38-year-old woman with chronic cough for mo re than 20 years. FDG PET revealed a hypermetabolic lesion with a lesi on-to-background ratio of 8.0 at the posterior aspect of the right mid dle lung. She underwent thoracotomy and tumor resection, and was diagn osed with cryptococcosis. The second case was that of a 72-year-old wo man who had pulmonary tuberculosis previously with cavitation in the l eft lower lobe. She suffered from fever, chills and severe hemoptysis for several days before this admission. FDG PET revealed a hypermetabo lic ring at the periphery of the cavity. The lesion-to-background rati o was 7.8. Echo-guided biopsy showed no evidence of malignancy. She wa s treated with antibiotics and the symptoms subsided gradually. Lung a bscess complicating a pre-existing cavity was diagnosed. These two cas es substantiate that positive FDG PET results should be interpreted wi th caution in differentiating benign from malignant pulmonary abnormal ities, especially in regions with a high prevalence of granulomatous l esions.