title: False-positive F-18 FDG uptake in PET/CT studies in pediatric patients with abdominal Burkitt's lymphoma.
abstract: BACKGROUND
  In pediatric patients with abdominal Burkitt's lymphoma, the involvement of the gastrointestinal tract and abdominal lymph nodes are the main presenting feature of the disease. Chemotherapy is the main treatment modality and could be preceded by surgical excision of the abdominal masses. To achieve cure or long-term disease-free survival a balance has to be struck between aggressive chemotherapy and the probability of tumor necrosis secondary to treatment complicated by acute infections, perforation or intestinal bleeding. F-18 fluorodeoxyglucose-positron emission tomography/computed tomography (F-18 FDG-PET/CT) has been recommended over conventional imaging modalities for the follow-up of these patients and for monitoring treatment response. As the incidences of postchemotherapy complications are high, the positive predictive value of PET/CT studies in these patients is very low and the false-positive rate is high from acute infections and tumor necrosis. Accordingly, histopathological confirmation of positive lesions on F-18 FDG-PET/CT studies is essential. This is especially important as post-therapy complications might present with nonspecific and nonurgent symptoms. At the same time initiating a second course of salvage chemotherapy is risky.
  
  
  OBJECTIVE
  Retrospectively reviewed F-18 FDG-PET/CT studies for 28 pediatric patients with abdominal Burkitt's lymphoma and diffuse large B-cell lymphoma after their treatment with chemotherapy or surgery.
  
  
  RESULTS
  Four positive studies were found. All had pathological verification and were because of acute inflammation and tumor necrosis and there was no evidence of viable tumor cells. One patient had multiple recurrent lesions in the abdomen after the initial surgical excision and before starting chemotherapy. The incidence of acute complications in this series is 10.7%.
  
  
  CONCLUSIONS
  This study confirms the high incidence of tumor necrosis and inflammation after chemotherapy for the abdominal Burkitt's lymphoma and consequently, the incidence of true-positive F-18 FDG studies is low. This necessitates the need for histopathological confirmation of positive studies.
authors.affiliation: Department of Nuclear Medicine, Children's Cancer Hospital, Cairo, Egypt.
authors.forename: Raef
authors.initials: R
authors.lastname: Riad
authors.forename: Walid
authors.initials: W
authors.lastname: Omar
authors.forename: Iman
authors.initials: I
authors.lastname: Sidhom
authors.forename: Manal
authors.initials: M
authors.lastname: Zamzam
authors.forename: Iman
authors.initials: I
authors.lastname: Zaky
authors.forename: Magdy
authors.initials: M
authors.lastname: Hafez
authors.forename: Hussein M
authors.initials: HM
authors.lastname: Abdel-Dayem
mesh_terms: D002051:Burkitt Lymphoma / Q000000981:diagnostic imaging*; D002648:Child; D002675:Child, Preschool; D005189:False Positive Reactions; D005260:Female; D019788:Fluorodeoxyglucose F18 / Q000494:pharmacology*; D006801:Humans; D008228:Lymphoma, Non-Hodgkin / Q000000981:diagnostic imaging; D008297:Male; D009336:Necrosis; D049268:Positron-Emission Tomography / Q000379:methods*; D019275:Radiopharmaceuticals / Q000494:pharmacology*; D015203:Reproducibility of Results; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed / Q000379:methods*
chemical_list: D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18