BACKGROUND:
Solitary Pulmonary Nodule (SPN) is one of the most common diagnostic problems in chest radiology because differentiation between benign and malignant nature of the lesions based on radiologic pictures may be difficult and sometimes impossible.
Nowadays, CT scan is the most accurate imaging modality for diagnosis and characterization of pulmonary nodules.

METHODS:
In this study, 131 patients were included in whom Preliminary chest x-ray revealed SPN, chest CT scan was the next imaging investigation in these patients.
Chest CT Scan confirmed SPN in 103 patients. Of these patients, Fine Needle Aspiration (FNA) and surgical resection of the nodule were taken place in 69 and 27 patients respectively. Pathological results compared with CT scan findings.

FINDINGS:
Considering CT characteristics of the lesions, results were in favor of malignancy in 27 patients and in other 61 patients, CT scan findings were consistent with benign process. Mentioned data disclosed sensitivity and specificity of CT scan in prediction of malignant SPN 81/8% and 86/3% respectively.

CONCLUSION:
CT scan as used in this study could be useful for determining benign or malignant nature of solitary pulmonary nodules. Rate of enhancement in the lesions following IV administration of contrast agent is the most important criterion to differentiate benign and malignant lesions.

KEY WORDS:
Solitary Pulmonary Nodule, CT scan