Comparison of 18F-FDG-PET/CT scans in patients diagnosed with sarcoidosis and tuberculosis

Positron emission tomography/computed tomography (PET/CT) is widely used to differentiate benign and malignant lesions. However, increased fluorodeoxyglucose (FDG) uptake may occur under certain benign conditions, leading to potential false positives in malignancy assessments. Tuberculosis and sarcoidosis are 2 conditions that can exhibit FDG uptake, presenting with both lymph node and extrathoracic involvement, alongside pulmonary manifestations. This study aimed to explore the utility of PET/CT in distinguishing between thoracic and extrathoracic involvement in patients with sarcoidosis and tuberculosis. A retrospective analysis was conducted on patients diagnosed with sarcoidosis or tuberculosis, either pathologically or microbiologically, who underwent ¹⁸F-FDG-PET/CT as part of their diagnostic process. This study evaluated demographic data, PET/CT findings, involvement sites, and maximum standardized uptake values (SUVmax) in patients with tuberculosis and sarcoidosis. PET/CT images of 62 patients (44 with tuberculosis and 18 with sarcoidosis) were analyzed. The median patient age was 55 years. Lymph node involvement in the cervical, abdominal, retro-pancreatic, inguinal, and extrathoracic regions was significantly more prevalent in patients with sarcoidosis than in those with tuberculosis (50% vs 20.5%, P = .0031; 27.8% vs 4.5%, P = .018; 22.2% vs 0%, P = .005; 27.8% vs 6.8%, P = .039; and 66.7% vs 27.3%, P = .009, respectively). No statistically significant difference was found in SUV values between patients with tuberculosis and those with sarcoidosis with regard to mediastinal lymph node, extrathoracic lymph node, lung, and bone PET/CT involvement. In conclusion, ¹⁸F-FDG-PET/CT imaging does not appear to be a reliable method for differentiating sarcoidosis and tuberculosis from malignant lesions, as it is not feasible to distinguish between sarcoidosis and tuberculosis solely based on ¹⁸F-FDG-PET/CT SUVmax values. Nevertheless, the increased prevalence of extrathoracic lymph node involvement in sarcoidosis compared to tuberculosis may offer valuable insights for clinicians in differential diagnosis.