title: Usefulness and pitfalls of F-18-FDG PET/CT for diagnosing extramedullary acute leukemia.
abstract: OBJECTIVE
  It is very important to identify whether there is extramedullary involvement in acute leukemia (AL), especially in those with recurrent disease. This retrospective study aimed to assess the role of (18)F-FDG PET/CT for diagnosing extramedullary AL.
  
  
  METHODS
  PET/CT examinations were performed in 9 patients with newly diagnosed AL, and 70 patients suspected to have recurrent AL. All the patients were diagnosed with AL by bone marrow biopsy. The diagnosis of extramedullary lesions was established according to the combination of pathology, physical examination, and imaging techniques including magnetic resonance imaging (MRI) and PET/CT, and/or cerebrospinal fluid (CSF) cytologic testing, and clinical follow-up.
  
  
  RESULTS
  Of the 79 patients, including 34 acute lymphocytic leukemia (ALL) and 45 acute myeloid leukemia (AML) cases, 30 patients were diagnosed with extramedullary AL. (18)F-FDG PET/CT demonstrated (18)F-FDG positive lesions in the extramedullary regions in 42 patients. Among them, 28 patients were diagnosed to have extramedullary AL and the other 14 were diagnosed with non-hematological malignancies (false positive disease). The sensitivity, specificity, and accuracy of (18)F-FDG PET/CT in diagnosing extramedullary involvement of AL were 93.3% (28/30), 71.4% (35/49), and 79.7%, respectively. The (18)F-FDG uptake of lesions was not significantly different between extramedullary AL and false positive cases (SUVmax: 6.66 ± 2.65 vs. 5.85 ± 1.88, t=1.275, P=0.206). The FDG uptake of extramedullary AL between ALL and AML were also not significantly different (SUVmax: 7.01 ± 2.82 vs. 6.10 ± 2.29, t=1.332, P=0.188). The predominant locations of extramedullary AL were the spleen, soft tissue, lymph nodes, central nerve system, liver, testis, and kidney. A total of 48.2% (27/56) of extramedullary AL lesions presented as diffuse FDG uptake compared with 6.25% (1/16) in the false positive lesions (χ(2)=9.221, P=0.002).
  
  
  CONCLUSIONS
  (18)F-FDG PET/CT is a sensitive, but not specific imaging modality for diagnosing extramedullary AL. Diffuse (18)F-FDG uptake in extramedullary lesions may indicate leukemia involvement.
authors.affiliation: NanFang PET Center, Nanfang Hospital, Southern Medical University, 1838 Guangzhou Avenue North, Guangzhou, Guangdong Province 510515, China. Electronic address: wenlanzhou@163.com.
authors.forename: Wen-Lan
authors.initials: WL
authors.lastname: Zhou
authors.affiliation: NanFang PET Center, Nanfang Hospital, Southern Medical University, 1838 Guangzhou Avenue North, Guangzhou, Guangdong Province 510515, China. Electronic address: wuhbym@163.com.
authors.forename: Hu-Bing
authors.initials: HB
authors.lastname: Wu
authors.affiliation: NanFang PET Center, Nanfang Hospital, Southern Medical University, 1838 Guangzhou Avenue North, Guangzhou, Guangdong Province 510515, China.
authors.forename: Li-Juan
authors.initials: LJ
authors.lastname: Wang
authors.affiliation: NanFang PET Center, Nanfang Hospital, Southern Medical University, 1838 Guangzhou Avenue North, Guangzhou, Guangdong Province 510515, China.
authors.forename: Ying
authors.initials: Y
authors.lastname: Tian
authors.affiliation: NanFang PET Center, Nanfang Hospital, Southern Medical University, 1838 Guangzhou Avenue North, Guangzhou, Guangdong Province 510515, China.
authors.forename: Ye
authors.initials: Y
authors.lastname: Dong
authors.affiliation: NanFang PET Center, Nanfang Hospital, Southern Medical University, 1838 Guangzhou Avenue North, Guangzhou, Guangdong Province 510515, China. Electronic address: wqslph@163.net.
authors.forename: Quan-Shi
authors.initials: QS
authors.lastname: Wang
mesh_terms: D000208:Acute Disease; D000293:Adolescent; D000328:Adult; D000368:Aged; D002648:Child; D002675:Child, Preschool; D005260:Female; D019788:Fluorodeoxyglucose F18; D006801:Humans; D007938:Leukemia / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D064847:Multimodal Imaging / Q000379:methods*; D049268:Positron-Emission Tomography / Q000379:methods*; D019275:Radiopharmaceuticals; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed / Q000379:methods*; D051598:Whole Body Imaging / Q000379:methods*; D055815:Young Adult
chemical_list: D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18
keywords: (18)F-FDG; Acute leukemia; Diagnosis; Extramedullary; PET/CT