The solitary pulmonary nodule(SPN) presents a diagnostic dilemma to the physician and the patients in the our nation with high incidence of tuberculoma. We could not exclude whether the SPN was benign or malignant by the change of the size at chest radiograph and findings of chest CT. Recently, positron emission tomography(PET) have been tried as the differential diagnostic method of SPN. We evaluated the efficacy of PET for differentiating malignant from benign SPN and the relationship between standardized uptake values(SUV) of PET and serum glucose.

Between January 2001 and July 2002, sixty-one patients with pulmonary nodule were examined by the chest CT and PET. The SPN has been finally diagnosed by the transthorasic needle aspiration and biopsy, bronchoscopic biopsy, and open lung biopsy.

Forty eight patients had a malignant nodule(23 squamous cell lung carcinoma, 16 adenocarcinoma, 9 small cell lung cancer) and thirteen patients had a benign nodule(3 tuberculoma, 9 inflammatory granuloma, 1 cryptococcosis). The mean size of malignant and benign nodule was 40.6 mm and 20.0 mm, respectively. All malignant nodules showed a marked increase in 18 fluorodeoxyglucose (FDG) uptake. Mean SUV of malignant was 9.52±5.20 and benign nodule was 1.61±3.60. There were false positive cases with an increase in 18-FDG uptake (2 tuberculoma, 1 inflammatory granuloma). The SUV of malignant nodule in diabetes patients has no difference in non diabetes patients(9.10±4.51 vs 9.65±5.46). The sensitivity and specificity of the PET scan for SPN were 100%, 77%, respectively. The positive and negative predictive values were 94% and 100%.

PET scanning showed highly accurate result in differentiating the malignant and benign SPN. There were no significant differences between the SUV and serum glucose in the patients with lung cancer.