False positive PET scan deserves attention

Pulmonary focal lesions are frequently identified incidentally. Furthermore, a final diagnosis is really a considerable problem for patients having risk factors for malignancy or particularly for a newly detected nodule during the postoperative period after any kind of lung surgery. For treatment decisions, the nature of the lesions needs to be clarified. Relatively recently positron emission tomography (PET) scan has been introduced as a non-invasive imaging method for the diagnosis of lesions on the basis of metabolic activity.

In this study 19 cases with false-positive nodules on PET scan are presented. Chest x-rays and thoracic computed tomographies (CT) were performed to all patients. Due to abnormal/suspicious lesions on radiologic imagies, PET scan was performed to these patients and high standard uptake values (SUV) above the cut-off value of 2.5 were suggestive of malignancy. Invasive procedures were performed to the patients with high suspicion of malignancy.

Histology of the resected lesions showed that all of them were benign and therefore the PET results were false-positive. The final diagnoses were tuberculosis, aspergilloma, bronchiolitis obliterans organizing pneumonia (BOOP), sarcoidosis, sequestration, anthracosis and hamartoma.

Patients living especially in countries with a high incidence of granulomatous diseases like tuberculosis, or patients in postoperative periods with high SUV should be studied thoroughly for false-positive PET results.