title: Differentiating between atypical adenomatous hyperplasia and bronchioloalveolar carcinoma using the computed tomography number histogram.
abstract: BACKGROUND
  Both atypical adenomatous hyperplasia (AAH) and bronchioloalveolar carcinoma (BAC) appear as ground glass opacity (GGO) lesions by computed tomography (CT) and are sometimes difficult to differentiate. To aid distinction between the two, we examined their CT number histograms.
  
  
  METHODS
  Histograms of pixel CT numbers were made for AAH (n = 9) and nonmucinous BAC (n = 8), and the peak and mean CT numbers on the histogram were quantified.
  
  
  RESULTS
  Although there was no significant difference in lesion size between AAH and BAC, all AAHs were less than or equal to 1 cm in diameter. All AAHs and BACs manifested one histogram peak. Both the peak and mean CT numbers on the histogram were significantly lower for AAH than for BAC (p < 0.001). However, the degree of overlap between AAH and BAC was less for the peak CT number than for the mean CT number.
  
  
  CONCLUSIONS
  The peak CT number on the histogram can help the radiologic differentiation between AAH and BAC. GGO lesions less than or equal to 1 cm in diameter that are diagnosed as AAH from the CT number histogram can be safely followed by CT.
authors.affiliation: Department of Thoracic Surgery, Saiseikai Central Hospital, Tokyo, Japan. hnomori@qk9.so-net.ne.jp
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Nomori
authors.forename: Takashi
authors.initials: T
authors.lastname: Ohtsuka
authors.forename: Tsuguo
authors.initials: T
authors.lastname: Naruke
authors.forename: Keiichi
authors.initials: K
authors.lastname: Suemasu
mesh_terms: D002282:Adenocarcinoma, Bronchiolo-Alveolar / Q000000981:diagnostic imaging*; D000236:Adenoma / Q000000981:diagnostic imaging*; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D006965:Hyperplasia; D008168:Lung / Q000000981:diagnostic imaging* / Q000473:pathology*; D008175:Lung Neoplasms / Q000000981:diagnostic imaging*; D008297:Male; D008875:Middle Aged; D014057:Tomography, X-Ray Computed / Q000706:statistics & numerical data*