title: The histologic grading of cancer.
abstract: BACKGROUND
  The histologic grade of a tumor provides prognostic information in addition to that provided by stage of disease. Poorly differentiated tumors are known to pursue a more aggressive course than their well differentiated counterparts.
  
  
  METHODS
  The frequency of grading and the relationship of grade to outcome was investigated for 793,649 cases of cancer from 15 anatomic sites as recorded in the Surveillance, Epidemiology, and End Results Program.
  
  
  RESULTS
  For all cancers, the frequency of grading increased from 1973 to 1987 and varied by anatomic site and histologic type. Survival decreased with advancing grade, and within each stage, grading separated cases into at least three distinct prognostic subgroups. For some cancers, regional stage cases assigned Grade 1 or 2 had higher survival rates than did localized stage cases assigned Grade 3 or 4. Therefore, grading allowed the identification of high and low risk subgroups within each stage grouping.
  
  
  CONCLUSIONS
  The tumor grade was a strong prognostic indicator for cancers of the urinary bladder, endometrium, and prostate--sites most often graded by pathologists. The histologic grade was also an important determinant of outcome for cancers of the brain, soft tissue, and breast; however, only a small percentage of these tumors were graded. The results are important because no common criteria for grading were established among the many contributing pathologists. Therefore, observer variation did not alter the known relationship of histologic grade to outcome. This review demonstrates that the histologic grade is a strong predictor of outcome that refines the prognostic information provided by the stage of disease.
authors.affiliation: Department of Pathology, Georgetown University School of Medicine, Washington, DC.
authors.forename: M T
authors.initials: MT
authors.lastname: Carriaga
authors.forename: D E
authors.initials: DE
authors.lastname: Henson
mesh_terms: D005260:Female; D006801:Humans; D008297:Male; D009367:Neoplasm Staging; D009369:Neoplasms / Q000453:epidemiology* / Q000473:pathology*; D011379:Prognosis; D018426:SEER Program; D014481:United States / Q000453:epidemiology