Solitary Pulmonary Nodules

Abstract

150,000 solitary pulmonary nodules (SPN), defined as single rounded lung lesions not associated with any other lung lesions or lymph-adenopathy, measuring ≤3 cm in maximal diameter, are diagnosed annually in the United States. PET imaging with FDG has largely focused on characterizing “indeterminate” SPNs as malignant or benign. The incidence of malignancy exceeds 40% in the large majority of reports. Benign SPNs might represent granuloma, infections, carcinoid, adenoma, hamartoma, fibrosis, and others. Bronchogenic carcinoma represents the majority of malignant solitary pulmonary nodules. The considerable number of benign solitary pulmonary nodules implies that a large number of biopsies performed are unnecessary. For example, 20% to 40% of lung biopsies produce benign tissue but result in significant morbidity. The diagnostic sensitivity and specificity of PET alone for characterizing solitary pulmonary nodules is high. PET is cost-effective for characterizing solitary pulmonary nodules. Because Medicare reimburses PET/CT at the same level as PET, these cost-effectiveness data also apply to PET/CT. PET/CT can be especially helpful for characterizing small lung nodules with only mildly increased glycolytic activity. The sensitivity of PET declines significantly, however, when solitary nodules are smaller than 8 mm.