title: Internal growth of nonsolid lung nodules: radiologic-pathologic correlation.
abstract: OBJECTIVE
  To determine whether computed tomographic (CT) attenuation values correlate with the histologic measurements of a lung cancer manifesting as a nonsolid nodule and to quantify the extent to which the tumor replaces the airspace within the nodule.
  
  
  METHODS
  Informed consent was obtained to analyze images from CT and pathologic examination under an institutional review board-approved protocol. Fifteen patients who had undergone resection of nonsolid lung cancer were evaluated. On the basis of the CT attenuation values of nonsolid nodules, nonneoplastic lung, soft tissue, and air, the overall proportion of soft tissue in the nodule and nonneoplastic lung and the difference between these two measures were calculated. The analogous measures were obtained from a representative digitized histologic slide. The area of each nodule and the proportion of air within it were measured, and the proportion of soft tissue in the nodule and nonneoplastic lung and the difference between the two were calculated. The difference between the two proportions at CT and histologic examination are the proportions attributable to the cancer on the basis of CT and histologic examinations, respectively. Linear regression was performed to assess the relationship between these measures.
  
  
  RESULTS
  The average proportions of soft tissue in the nodule at CT and histologic examination were 48% and 69%, respectively, and they showed significant correlation with each other (P = .02); in addition, each showed significant correlation with the attenuation of the nodule (P < .0001 and P = .02, respectively). The difference between the proportions of soft tissue in nodule and nonneoplastic lung at CT and histologic examination were 37% and 30%, respectively, and both were independent of the tumor diameter (P = .26 and P = .41).
  
  
  CONCLUSIONS
  The proportion of soft tissue within a nonsolid nodule is correlated with attenuation at CT. This allows for measurement of change within the nodule. An increase of 100 HU in nodule attenuation represents an approximately 10% increase in tumor volume.
authors.affiliation: Department of Radiology, Mount Sinai School of Medicine, New York, NY 10029, USA.
authors.forename: Lijuan
authors.initials: L
authors.lastname: Zhang
authors.forename: David F
authors.initials: DF
authors.lastname: Yankelevitz
authors.forename: Darryl
authors.initials: D
authors.lastname: Carter
authors.forename: Claudia I
authors.initials: CI
authors.lastname: Henschke
authors.forename: Rowena
authors.initials: R
authors.lastname: Yip
authors.forename: Anthony P
authors.initials: AP
authors.lastname: Reeves
mesh_terms: D000230:Adenocarcinoma / Q000000981:diagnostic imaging* / Q000473:pathology* / Q000601:surgery; D006801:Humans; D016014:Linear Models; D008175:Lung Neoplasms / Q000000981:diagnostic imaging* / Q000473:pathology* / Q000601:surgery; D003074:Solitary Pulmonary Nodule / Q000000981:diagnostic imaging* / Q000473:pathology* / Q000601:surgery; D014057:Tomography, X-Ray Computed / Q000379:methods*