title: Intratumoral heterogeneity of F-18 FDG uptake differentiates between gastrointestinal stromal tumors and abdominal malignant lymphomas on PET/CT.
abstract: OBJECTIVE
  Gastrointestinal stromal tumors (GISTs) and malignant lymphomas (MLs) in the abdomen are often observed as tumors of unknown origin on F-18 FDG PET/CT. The purpose of this study was to evaluate the intratumoral metabolic heterogeneity of F-18 FDG uptake on PET to determine if it might be helpful to discriminate between these tumors.
  
  
  METHODS
  The F-18 FDG PET/CT findings of 21 large abdominal tumors were retrospectively evaluated (9 GISTs and 12 MLs). Intratumoral heterogeneity was evaluated by visual scoring (visual score: 0, homogeneous; 1, slightly heterogeneous; 2, moderately heterogeneous; 3, highly heterogeneous) and by the cumulative standardized uptake value (SUV) histograms on transaxial PET images at the maximal cross-sectional tumor diameter. Percent tumor areas above a threshold from 0 to 100% of the maximum SUV were plotted and the area under curve of the cumulative SUV histograms (AUC-CSH) was used as a heterogeneity index, where lower values corresponded with increased heterogeneity. Correlation between the visual score and the AUC-CSH was investigated by the Spearman's rank test.
  
  
  RESULTS
  GISTs exhibited heterogeneous uptake of F-18 FDG, whereas MLs showed rather homogeneous uptake on visual analysis (visual score: 2.67 ± 0.50 and 0.58 ± 0.79, respectively; p < 0.001). The AUC-CSH was significantly lower for the GISTs than for the MLs (0.41 ± 0.14 and 0.64 ± 0.08, respectively; p < 0.001). Significant correlations were observed between the visual score and the AUC-CSH (ρ = -0.866, p < 0.001).
  
  
  CONCLUSIONS
  GISTs exhibited significantly heterogeneous intratumoral tracer uptake as compared with the MLs. Evaluation of the intratumoral heterogeneity of F-18 FDG uptake may help in the discrimination between these tumors.
authors.affiliation: Department of Nuclear Medicine and Tracer Kinetics, Osaka University Graduate School of Medicine, Yamadaoka, Suita, Osaka, Japan.
authors.forename: Tadashi
authors.initials: T
authors.lastname: Watabe
authors.forename: Mitsuaki
authors.initials: M
authors.lastname: Tatsumi
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Watabe
authors.forename: Kayako
authors.initials: K
authors.lastname: Isohashi
authors.forename: Hiroki
authors.initials: H
authors.lastname: Kato
authors.forename: Masahiro
authors.initials: M
authors.lastname: Yanagawa
authors.forename: Eku
authors.initials: E
authors.lastname: Shimosegawa
authors.forename: Jun
authors.initials: J
authors.lastname: Hatazawa
mesh_terms: D000008:Abdominal Neoplasms / Q000000981:diagnostic imaging* / Q000378:metabolism; D001692:Biological Transport; D003937:Diagnosis, Differential; D005260:Female; D019788:Fluorodeoxyglucose F18 / Q000378:metabolism*; D005770:Gastrointestinal Neoplasms / Q000000981:diagnostic imaging* / Q000378:metabolism; D046152:Gastrointestinal Stromal Tumors / Q000000981:diagnostic imaging* / Q000378:metabolism; D006801:Humans; D008223:Lymphoma / Q000000981:diagnostic imaging* / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D064847:Multimodal Imaging; D049268:Positron-Emission Tomography; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed
chemical_list: D019788:Fluorodeoxyglucose F18