PET/CT in pediatric lymphoma is more accurate than CIM. We recommend that it should be the first modality for all purposes in initial staging, evaluating treatment response and follow-up.

Purpose The aim of this study was to explore the positive predictive value and negative predictive value of FDG PET/CT. The prognostic impact of tumor burden of bone marrow infiltrates was diagnosed by FDG PET/CT at initial presentation. Methods This retrospective study enrolled 140 pediatric patients with pathologically proven lymphoma (113 Hodgkin disease and 27 Non-Hodgkin lymphoma). All patients had pretherapy FDG PET/CT. Bone marrow biopsy (BMB), clinical, radiological, and follow-up data were also collected. The skeleton was divided into 8 segments, and a 5-point scoring system was used for assessment of BM infiltration burden. Results Among the 140 lymphoma patients, FDG PET/CT revealed positive BM involvement in 41 patients; 2 of them were false-positive with negative BMB and regional MRI results. Positive predictive value was 95.1% for PET/CT compared with 100% with BMB. All patients diagnosed with positive BMI by BMB were detected by FDG PET/CT. On the contrary, BMB missed 25 patients (17.9%) with statistically significant difference. Negative predictive value was 100% for PET/CT compared with 80.2% for BMB (P < 0.05). FDG PET/CT upstaged 17.9% of the enrolled patients. Bone marrow involvement based on the 5-point scoring system was assessed. No significant difference was demonstrated in therapy outcome between patient with focal BMI (score 2) and extensive BMI (score 5; P = 0.06). Conclusions FDG PET/CT has optimum negative predictive value compared with BMB in detection of bone marrow infiltrations in pediatric lymphoma with upstaging cases missed with BMB. Prognostic impact of BMI based on the 5-point scoring system reveals that the main influence is presence or absence of BMI rather than its tumor burden.

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Objectives: To demonstrate the value of FDG PET/CT in evaluation of childhood patient with osseous Langerhans cell histiocytosis (LCH). Patients and Methods: A prospective analysis of 24 pediatric patients with histopathologically proven LCH September 2016 till November 2018. All patients received specific therapy for LCH in the form of chemotherapy &/or surgical resection. Analysis criteria included the following: any focal FDG uptake was considered abnormal when it was greater than that of hepatic uptake or in presence of abnormal changes on CT with any degree of FDG uptake. Results: 17 patients (70.8%) presented with multi-system disease (bone as well as LNs &/or liver, lungs, soft tissue and skin), 5 patients (20.8%) had uni-focal osseous lesions and 2 patients (8.3%) presented by multi-focal bone lesions. FDG PET/CT revealed metabolic changes in osseous lesions detected by anatomical radiographic scan and revealed multiple other lesions as well. No statistically significant association could be detected between neither disease recurrence nor risk of mortality at diagnosis with age, sex, presenting organ, disease extent, risk of mortality, SUV max of leading lesion. Conclusion: PET/CT may be useful as additional imaging to assess known LCH lesions and rule out the presence of other organ infiltration and to provide a reference basis of staging, treatment plan.