PET/CT is successfully used in metabolic characterization of lung nodules in adult patients. An SUV max of 2.5 is generally accepted to distinguish benign from malignant lesions; for small solitary lung nodules some authors recommend visual evaluation rather than only SUV, suggesting that classical SUV criterion of 2.5 is inappropriate.

In pediatric patients interpretation of nodular opacity is still a clinical problem: specificity of CT in a pulmonary nodule, especially when small, is still limited.

Aim of this prospective study was to evaluate PET/ CT for non invasive characterization of pulmonary nodules in pediatric bone sarcomas.

Materials and methods: 56 whole-body PET-CT exams were performed in 19 patients with OS (14 female, 5 male) and 9 with ES (4 female and 5 male); median age at the first PET/CT exam was 14 years 8 months. PET/ CT results have been correlated with conventional imaging (CI), hystologic findings and clinical follow-up.

Results: PET/CT correctly identified pulmonary metastases, according with CI, in 33/56 exams (59%), PET/ CT revealed correctly “understaging” in 15 exams (27%) (10 in ES, 5 in OS) and incorrect “understaging” in 8 (14%) exams (4 in OS, 4 in ES). There were no false positive in either groups.

Conclusion: Correct diagnosis of a pulmonary opacity is fundamental for prognosis and choice of treatment in patients with doubtful lung lesions. Our preliminary results suggest the feasibility of a correct characterization by PET/CT in paediatric bone sarcoma patients. In particular PET/CT seems accurate and sensitive for lung nodules higher than 5 mm: an SUV max (and SUV ratio) higher than 1 seems to be significant when size is higher than 5 mm, while no significant SUV max (and SUV ratio) differences were found for smaller lesions.

Prospective studies are needed to clarify benefit of PET/CT in management of these patients.