title: Risk of breast cancer in women with breast cysts.
abstract: OBJECTIVE
  To study the occurrence of breast cancer in women with breast cysts.
  
  
  METHODS
  Prospective follow-up study.
  
  
  METHODS
  Office surgical practice.
  
  
  METHODS
  All 742 women referred to the practice with breast cysts diagnosed by means of aspiration or, occasionally, biopsy between 1969 and 1985.
  
  
  METHODS
  The incidence of breast cancer and the number of years between diagnosis of breast cyst and diagnosis of cancer. The observed number of cases of breast cancer was compared with the expected number, calculated from Ontario rates of breast cancer.
  
  
  RESULTS
  Fifteen of the women died but did not have breast cancer. No follow-up information was available for five women. Another 38 were lost to follow-up; they did not have breast cancer at the last contact, after 2 to 17 years of follow-up. These patients were withdrawn from the study in the year in which they died or were last observed. By 1990, 34 (5%) of the women had breast cancer. The overall ratio of observed:expected cases of cancer was 3.04 (95% confidence interval 2.09 to 4.28). Breast cancer developed after 7.5 years, but the average length of follow-up was only 10.1 years. Only 3.8% of 374 women after 10 years and 5.4% of 141 women after 15 years had breast cancer.
  
  
  CONCLUSIONS
  Women who have a gross breast cyst are at moderately increased risk of breast cancer, which usually develops only after many years.
authors.affiliation: Department of Surgery, Ottawa Civic Hospital, Ont.
authors.forename: J E
authors.initials: JE
authors.lastname: Devitt
authors.forename: T
authors.initials: T
authors.lastname: To
authors.forename: A B
authors.initials: AB
authors.lastname: Miller
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001943:Breast Neoplasms / Q000453:epidemiology* / Q000209:etiology; D005260:Female; D005348:Fibrocystic Breast Disease / Q000150:complications*; D005500:Follow-Up Studies; D006801:Humans; D015994:Incidence; D008875:Middle Aged; D009864:Ontario / Q000453:epidemiology; D011446:Prospective Studies; D012307:Risk Factors