Accuracy of 18-FDG PET/CT in the Differential Diagnosis of Malignant and Benign Pleural Diseases

Integrated whole-body 18-fluorodeoxyglucose positron emission tomography-computed tomography (PET/CT) is a non-invasive imaging technique for identifying several types of malignant diseases. We evaluated the role of PET/CT in distinguishing malignant from benign pleural diseases. Thirty patients, who had pleural abnormalities on computed tomography (CT), such as thickening, fluid with suspicion of malignant pleural mesothelioma or any other malignancy underwent PET/CT. Maximum standardized uptake values (SUVmax) were calculated separately for pleural thickening and pleural fluid and compared with pathological results obtained by video thoracoscopy. Twenty-two patients with pleural thickening and 25 patients with pleural fluid were assessed with regard to the accuracy of PET/CT. The overall sensitivity,specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy of PET/CT was 81.8%, 54.5%, 64.3%, 75%, and 68.2% for pleural thickening and it was 100%, 56.5%, 41.1%, 100%, and 60% for patients with pleural fluid. When the pleural thickening was evaluated, the SUVmax values were higher in the malignant pleural diseases than in the benign pleural diseases but the difference was not statistically significantly (p = 0.063). When the pleural fluid was evaluated, the SUVmax values were also higher in the malignant pleural diseases than in the benign pleural diseases and the difference was statistically significantly (p= 0.03). The accuracy of PET/CT for detecting malignant pleural fluids was high. However, PET/CT was not adequate to make the differential diagnosis of pleural malignancies especially in case of pleural thickening because of its relatively low sensitivity,specificity,PPV, and NPV. A tissue biopsy is necessary to determine the diagnosis.