title: Visually isoattenuating pancreatic adenocarcinoma at dynamic-enhanced CT: frequency, clinical and pathologic characteristics, and diagnosis at imaging examinations.
abstract: OBJECTIVE
  To retrospectively determine the frequency, clinical and pathologic characteristics, and computed tomographic (CT) findings of visually isoattenuating pancreatic adenocarcinomas and to investigate the utility of magnetic resonance (MR) imaging and positron emission tomography (PET)/CT for detecting them.
  
  
  METHODS
  Institutional review board approval was obtained. Patient informed consent was waived. Of 743 consecutive patients with pathologically proved pancreatic cancer, 644 patients (392 men, 252 women; mean age, 60 years ± 9.5 [standard deviation]) who had undergone both arterial and portal phase contrast material-enhanced CT were included. Visually isoattenuating pancreatic adenocarcinoma was defined as lesion isoattenuation in both scan phases. Serum levels of carbohydrate antigen 19-9, immunoglobulin G (IgG), and IgG fraction 4 (IgG4), survival after curative-intent surgery; and pathologic findings of visually isoattenuating pancreatic adenocarcinomas were analyzed. CT findings of visually isoattenuating pancreatic adenocarcinomas and the sensitivity of MR imaging and PET/CT for detecting them were determined.
  
  
  RESULTS
  The frequency of visually isoattenuating pancreatic adenocarcinomas among pancreatic cancers was 5.4% (35 of 644). Serum levels of carbohydrate antigen 19-9, IgG, and IgG4 were elevated in 51.5% (17 of 33), 8.3% (one of 12), and 8.3% (one of 12) of patients, respectively. Visually isoattenuating pancreatic adenocarcinoma, compared with usual pancreatic adenocarcinoma, was independently associated with a better survival after curative-intent surgery: Adjusted hazard ratio was 0.430 (P = .006). Thirty surgically resected visually isoattenuating pancreatic adenocarcinomas were 1.5-4 cm (median, 3 cm). Their pathologic findings differed from those of usual pancreatic adenocarcinomas: lower tumor cellularity, more frequent intratumoral acinar tissue and islet cells, and less prominent tumor necrosis. Visually isoattenuating pancreatic adenocarcinomas showed various abnormalities at CT, which may suggest an isoattenuating mass or nodule. Sensitivities of MR imaging and PET/CT were 79.2% (19 of 24) and 73.7% (14 of 19), respectively.
  
  
  CONCLUSIONS
  Visually isoattenuating pancreatic adenocarcinoma represents a small but meaningful subset of pancreatic cancer and has characteristic clinical and pathologic features. MR imaging and PET/CT may be useful as subsequent examinations when the patient is suspected of having the lesion at CT.
authors.affiliation: Department of Radiology and Research Institute of Radiology, University of Ulsan College of Medicine, Asan Medical Center, Seoul, Korea.
authors.forename: Jin Hee
authors.initials: JH
authors.lastname: Kim
authors.forename: Seong Ho
authors.initials: SH
authors.lastname: Park
authors.forename: Eun Sil
authors.initials: ES
authors.lastname: Yu
authors.forename: Myung-Hwan
authors.initials: MH
authors.lastname: Kim
authors.forename: Jihun
authors.initials: J
authors.lastname: Kim
authors.forename: Jae Ho
authors.initials: JH
authors.lastname: Byun
authors.forename: Seung Soo
authors.initials: SS
authors.lastname: Lee
authors.forename: Hye Jeon
authors.initials: HJ
authors.lastname: Hwang
authors.forename: Jae-Yeon
authors.initials: JY
authors.lastname: Hwang
authors.forename: Sang Soo
authors.initials: SS
authors.lastname: Lee
authors.forename: Moon-Gyu
authors.initials: MG
authors.lastname: Lee
mesh_terms: D000230:Adenocarcinoma / Q000175:diagnosis* / Q000473:pathology / Q000601:surgery; D000328:Adult; D000368:Aged; D014408:Biomarkers, Tumor / Q000097:blood; D001706:Biopsy; D003287:Contrast Media; D005260:Female; D006801:Humans; D007472:Iohexol / Q000031:analogs & derivatives; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D010190:Pancreatic Neoplasms / Q000175:diagnosis* / Q000473:pathology / Q000601:surgery; D049268:Positron-Emission Tomography; D012189:Retrospective Studies; D012680:Sensitivity and Specificity; D016019:Survival Analysis; D014057:Tomography, X-Ray Computed
chemical_list: D014408:Biomarkers, Tumor; D003287:Contrast Media; D007472:Iohexol; C038192:iopromide