title: Thallium-201 Uptake of Giant Cell Tumor: One Step Toward the Differential Diagnosis to Atypically Presenting Osteosarcoma.
abstract: OBJECTIVE
  The radiologic differential diagnosis of giant cell tumors (GCTs) is challenging because there is a risk of misdiagnosis of GCTs as malignant lesions such as atypically presenting osteosarcomas (OSs). This study aims to assess the feasibility of201Tl scintigraphy for the differential diagnosis of GCT and atypical OS.
  
  
  METHODS
  Thallium-201 scintigraphy scans obtained between January 2006 and October 2015 of patients with histologically proven GCT (23 patients [male-to-female ratio, 15:8]; median age, 33.0 years; age range, 20-61 years) and patients with atypically presenting OS (20 patients [male-to-female ratio, 11:9]; median age, 30.0 years; age range, 12-69 years) were retrospectively reviewed. Morphologic classification of osseous lesions was performed on radiographs and CT scans. The201Tl scintigraphy-based tumor-to-background contrast (TBC) and washout rate (WR) were calculated on early phase and delayed phase scans. The laboratory parameters lactate dehydrogenase (LDH), C-reactive protein (CRP), and alkaline phosphatase were obtained. Statistical significance was estimated using the Mann-Whitney U test. Cutoff values were calculated for early phase TBC and delayed phase TBC.
  
  
  RESULTS
  Twenty-two of 23 GCTs were detected on the initial radiographs, whereas only six of 20 atypical OSs were detected on the initial radiographs. The early phase TBC was increased in GCT (median, 2.59; range, 0.51-12.26) compared with atypical OS (median, 1.68; range, 0.90-6.45) (p = 0.07). The delayed phase TBC was increased in GCT (median, 1.65; range, 0.22-5.26) compared with atypical OS (median, 0.96; range, 0.39-3.76) (p = 0.02). The median WR was not significantly decreased in GCT. The cutoff value for the early phase TBC was 3.90, and the cutoff value for the delayed phase TBC was 1.64; these cutoff values for early and delayed phase TBC yielded a sensitivity of 80.0% and a specificity of 47.8% and 52.2% respectively. Serum LDH (mean: atypical OS vs GCT, 215.5 vs 170.5 U/L, respectively; p = 0.01), alkaline phosphatase (median: 355.0 vs 252.0 U/L; p = 0.03), and CRP (median: 0.21 vs 0.09 mg/dL; p = 0.04) values were significantly increased in atypical OS compared with GCT.
  
  
  CONCLUSIONS
  The intense201Tl uptake of GCT in combination with laboratory OS biomarkers facilitate the differential diagnosis of GCT and atypically presenting OS.
authors.affiliation: 1 Department of Diagnostic and Interventional Radiology, University Medical Center Hamburg-Eppendorf, Martinistrasse 52, 20246 Hamburg, Germany.
authors.forename: Sarah
authors.initials: S
authors.lastname: Keller
authors.affiliation: 2 Department of Radiology, Okayama University Hospital, Okayama City, Okayama, Japan.
authors.forename: Ryota
authors.initials: R
authors.lastname: Inai
authors.affiliation: 2 Department of Radiology, Okayama University Hospital, Okayama City, Okayama, Japan.
authors.forename: Shuhei
authors.initials: S
authors.lastname: Sato
authors.affiliation: 2 Department of Radiology, Okayama University Hospital, Okayama City, Okayama, Japan.
authors.forename: Akihiro
authors.initials: A
authors.lastname: Tada
authors.affiliation: 1 Department of Diagnostic and Interventional Radiology, University Medical Center Hamburg-Eppendorf, Martinistrasse 52, 20246 Hamburg, Germany.
authors.forename: Gerhard
authors.initials: G
authors.lastname: Adam
authors.affiliation: 1 Department of Diagnostic and Interventional Radiology, University Medical Center Hamburg-Eppendorf, Martinistrasse 52, 20246 Hamburg, Germany.
authors.forename: Jin
authors.initials: J
authors.lastname: Yamamura
authors.affiliation: 2 Department of Radiology, Okayama University Hospital, Okayama City, Okayama, Japan.
authors.forename: Susumu
authors.initials: S
authors.lastname: Kanazawa
mesh_terms: D000328:Adult; D001859:Bone Neoplasms / Q000000981:diagnostic imaging / Q000378:metabolism*; D003937:Diagnosis, Differential; D005260:Female; D005870:Giant Cell Tumors / Q000000981:diagnostic imaging / Q000378:metabolism* / Q000473:pathology; D006801:Humans; D008297:Male; D008875:Middle Aged; D012516:Osteosarcoma / Q000000981:diagnostic imaging / Q000378:metabolism* / Q000473:pathology*; D019275:Radiopharmaceuticals / Q000493:pharmacokinetics; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D013794:Thallium Radioisotopes / Q000493:pharmacokinetics*; D055815:Young Adult
chemical_list: D019275:Radiopharmaceuticals; D013794:Thallium Radioisotopes
keywords: 201Tl scintigraphy; giant cell tumor; osteosarcoma; thallium; tumor-to-background contrast (TBC)