title: Sarcoid-like reaction to malignancy on whole-body integrated (18)F-FDG PET/CT: prevalence and disease pattern.
abstract: OBJECTIVE
  To evaluate the prevalence of sarcoid-like reaction to malignancy detected using integrated 2-[(18)F]-fluoro-2-deoxy-d-glucose (FDG) positron-emission tomography and computed tomography (PET/CT) in patients undergoing staging or restaging of solid-organ malignancy.
  
  
  METHODS
  A systematic search was performed using the institutional radiology information system of 2048 consecutive PET/CT examinations performed in cancer patients at a tertiary-referral centre. Cases that were considered suspicious for sarcoid-like reaction were identified from the initial radiological report and were retrospectively reviewed by three experienced PET/CT reporters.
  
  
  RESULTS
  Sarcoid-like reaction was initially suspected in 23 of the 2048 (1.1%) FDG PET/CT examinations, with the diagnosis confirmed histologically or by clinico-radiological follow-up in 13 of the 23 cases (57%). Sarcoid-like reaction was more commonly seen in patients undergoing FDG PET/CT for restaging of suspected recurrence rather than for primary tumour staging (77% versus 23%; p=0.05). The mean maximum standardized uptake value (SUV(max)) of confirmed hilar and mediastinal sarcoid-like reaction was 7.3 (range 3.1-13.6). Symmetric hilar uptake was demonstrated in 11 of the 13 (85%) and all 13 had additional mediastinal nodal uptake. Pulmonary uptake was seen in seven of the 13 cases (54%). Extra-thoracic involvement was present in eight of the 13 (61.5%), including nodal, splenic, and hepatic lesions.
  
  
  CONCLUSIONS
  Sarcoid-like reaction was suspected in 1.1% of cancer patients at FDG PET/CT examination, with confirmation of the diagnosis in 0.6%. With the increasing use of FDG PET/CT in cancer patients, it is important to be aware of the prevalence of this uncommon, but important, disease entity and to consider this diagnosis in appropriate cases in order to avoid a false-positive interpretation of metastatic disease.
authors.affiliation: Department of Radiology and Nuclear Medicine, Leeds Teaching Hospitals NHS Trust, Leeds, UK. fahmid.chowdhury@leedsth.nhs.uk
authors.forename: F U
authors.initials: FU
authors.lastname: Chowdhury
authors.forename: F
authors.initials: F
authors.lastname: Sheerin
authors.forename: K M
authors.initials: KM
authors.lastname: Bradley
authors.forename: F V
authors.initials: FV
authors.lastname: Gleeson
mesh_terms: D000328:Adult; D000368:Aged; D005260:Female; D019788:Fluorodeoxyglucose F18; D006099:Granuloma / Q000000981:diagnostic imaging / Q000473:pathology*; D006801:Humans; D008171:Lung Diseases / Q000473:pathology; D008297:Male; D008477:Mediastinal Diseases / Q000473:pathology; D008875:Middle Aged; D009367:Neoplasm Staging; D009369:Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology*; D049268:Positron-Emission Tomography / Q000379:methods; D015995:Prevalence; D019275:Radiopharmaceuticals; D012189:Retrospective Studies; D012507:Sarcoidosis / Q000000981:diagnostic imaging / Q000473:pathology*; D014057:Tomography, X-Ray Computed / Q000379:methods
chemical_list: D019275:Radiopharmaceuticals; D019788:Fluorodeoxyglucose F18