The role of F-18 FDG PET/CT in differentiating benign from malignant pulmonary masses and accompanying lymph nodes.

Introduction: The aim of this study was to evaluate the usefulness of SUV and lesion size to differentiate benign and malignant lesions of the lung and accompanying mediastinal lymph node on F-18 FDG PET/CT imaging.

Materials And Methods: A retrospective analysis was carried out on 100 patients with suspected lung cancer who were recommended for PET/CT scans for diagnosis and staging. The results of the SUV, lesion size and patient's age were compared with histopathology which was considered to be the 'gold standard' and sensitivity and specificity were calculated respectively. Lymph nodes greater than 1 cm in patients with benign pathology were evaluated and the SUV values were recorded.

Result: Of the 100 patients, 38 were found to have benign, whereas 62 had malignant on histopathology. The SUV was significantly more elevated in malign masses (13.1 ± 6.4) than in benign masses (8 ± 5.7) (p< 0.05). The dimensions of malignant masses (4.5 ± 2.5 cm) were larger than benign ones (3 ± 1.6 cm) (p< 0.05). SUV of 7.6 was determined as the cut-off value, while the sensitivity and specificity were 82% and 55% respectively. The sensitivity was 87% and specificity was 45% for the lesion sizes in differentiation of the malignant and benign lesions.

Conclusions: There are significant overlaps between benign and malignant lesions and specialists must be aware of the various pathological conditions that can give false positives and negatives.