RT Journal Article SR Electronic T1 Clinical Significance of Small Pulmonary Nodules with Little or No 18F-FDG Uptake on PET/CT Images of Patients with Nonthoracic Malignancies JF Journal of Nuclear Medicine JO J Nucl Med FD Society of Nuclear Medicine SP 15 OP 21 VO 48 IS 1 A1 Joo Hyun O A1 Ie Ryung Yoo A1 Sung Hoon Kim A1 Hyung Sun Sohn A1 Soo Kyo Chung YR 2007 UL http://jnm.snmjournals.org/content/48/1/15.abstract AB Small pulmonary nodules with little or no perceptible 18F-FDG uptake are relatively common findings on combined PET/CT images of patients with nonthoracic malignancies. Interpreting such nodules is often a diagnostic challenge, and this study aimed to evaluate the clinical significance of the nodules. Methods: Patients with pulmonary nodules ≤1 cm in diameter showing no 18F-FDG uptake or uptake less than the mediastinal background were included. Nodules with clearly benign or metastatic findings on CT were excluded. One hundred twenty-one patients had either tissue confirmation or clinical follow-up with additional chest images. The subjects were studied by 3 variables: (i) solitary versus multiple nodules, (ii) presence of accompanying benign lung lesion versus absence, and (iii) imperceptible 18F-FDG uptake versus faint 18F-FDG uptake. The malignancy rates were calculated for each variable. Results: Of the 121 patients, 24 had malignancy, with a strong possibility of pulmonary metastasis (19.8%). Six of the 44 patients with solitary nodules (13.6%) and 18 of the 77 patients with multiple nodules (23.4%) had malignancies, though there was no statistically significant difference in the incidences of malignancy between the solitary and multiple groups. On the other hand, there was a statistically significant difference (P = 0.040) between the accompanying lung lesion present (8.3%) and absent (24.7%) groups. No statistically significant difference was noted between the 18F-FDG uptake imperceptible group and faint 18F-FDG uptake group (20.7% vs. 17.2%). Conclusion: For patients with incidental lung nodules of indeterminate nature with no 18F-FDG uptake or uptake less than that of the mediastinum on PET/CT images, >19% of the cases turned out to be malignant. The nodule was more likely to be malignant when no other benign pulmonary lesions could be identified elsewhere in the lung field. Thus, regardless of the number of nodules and 18F-FDG uptake, tissue confirmation or close imaging follow-up is necessary when small nodules with imperceptible or faint 18F-FDG activity are present on the PET/CT images, especially in the absence of accompanying benign lung lesions.