title: Benign breast disease and the risk of breast cancer.
abstract: BACKGROUND
  Benign breast disease is an important risk factor for breast cancer. We studied a large group of women with benign breast disease to obtain reliable estimates of this risk.
  
  
  METHODS
  We identified all women who received a diagnosis of benign breast disease at the Mayo Clinic between 1967 and 1991. Breast-cancer events were obtained from medical records and questionnaires. To estimate relative risks, we compared the number of observed breast cancers with the number expected on the basis of the rates of breast cancer in the Iowa Surveillance, Epidemiology, and End Results registry.
  
  
  RESULTS
  We followed 9087 women for a median of 15 years. The histologic findings were nonproliferative lesions in 67 percent of women, proliferative lesions without atypia in 30 percent, and atypical hyperplasia in 4 percent. To date, 707 breast cancers have developed. The relative risk of breast cancer for the cohort was 1.56 (95 percent confidence interval, 1.45 to 1.68), and this increased risk persisted for at least 25 years after biopsy. The relative risk associated with atypia was 4.24 (95 percent confidence interval, 3.26 to 5.41), as compared with a relative risk of 1.88 (95 percent confidence interval, 1.66 to 2.12) for proliferative changes without atypia and of 1.27 (95 percent confidence interval, 1.15 to 1.41) for nonproliferative lesions. The strength of the family history of breast cancer, available for 4808 women, was a risk factor that was independent of histologic findings. No increased risk was found among women with no family history and nonproliferative findings. In the first 10 years after the initial biopsy, an excess of cancers occurred in the same breast, especially in women with atypia.
  
  
  CONCLUSIONS
  Risk factors for breast cancer after the diagnosis of benign breast disease include the histologic classification of a benign breast lesion and a family history of breast cancer.
authors: Division of Medical Oncology, Mayo Clinic College of Medicine, Rochester, MN 55905, USA.
authors: Lynn C
authors: LC
authors: Hartmann
authors: Thomas A
authors: TA
authors: Sellers
authors: Marlene H
authors: MH
authors: Frost
authors: Wilma L
authors: WL
authors: Lingle
authors: Amy C
authors: AC
authors: Degnim
authors: Karthik
authors: K
authors: Ghosh
authors: Robert A
authors: RA
authors: Vierkant
authors: Shaun D
authors: SD
authors: Maloney
authors: V Shane
authors: VS
authors: Pankratz
authors: David W
authors: DW
authors: Hillman
authors: Vera J
authors: VJ
authors: Suman
authors: Jo
authors: J
authors: Johnson
authors: Cassann
authors: C
authors: Blake
authors: Thea
authors: T
authors: Tlsty
authors: Celine M
authors: CM
authors: Vachon
authors: L Joseph
authors: LJ
authors: Melton
authors: Daniel W
authors: DW
authors: Visscher
mesh_terms: D000328:Adult; D017668:Age of Onset; D000368:Aged; D001940:Breast / Q000473:pathology*; D001941:Breast Diseases / Q000150:complications* / Q000473:pathology; D001943:Breast Neoplasms / Q000209:etiology* / Q000235:genetics; D015331:Cohort Studies; D005260:Female; D005348:Fibrocystic Breast Disease / Q000150:complications / Q000473:pathology; D006801:Humans; D006965:Hyperplasia / Q000150:complications; D008875:Middle Aged; D016016:Proportional Hazards Models; D012306:Risk