title: Timing of critical genetic changes in human breast disease.
abstract: BACKGROUND
  Breast cancer development has been characterized as a nonobligatory sequence of histological changes from normal epithelium through invasive malignancy. Although genetic alterations are thought to accumulate stochastically during tumorigenesis, little is known about the timing of critical mutations. This study examined allelic imbalance (AI) in tissue samples representing a continuum of breast cancer development to examine the evolution of genomic instability.
  
  
  METHODS
  Laser-microdissected DNA samples were collected from histologically normal breast specimens (n = 25), atypical ductal hyperplasia (ADH, n = 16), ductal carcinoma-in-situ (DCIS, n = 37), and stage I to III invasive carcinomas (n = 72). Fifty-two microsatellite markers representing 26 chromosomal regions commonly deleted in breast cancer were used to assess patterns of AI.
  
  
  RESULTS
  AI frequencies were <5% in histologically normal and ADH specimens, 20% in DCIS lesions, and approximately 25% in invasive tumors. Mann-Whitney tests showed (1) that levels of AI in ADH samples did not differ significantly from those in histologically normal tissues and (2) that AI frequencies in DCIS lesions were not significantly different from those in invasive carcinomas. ADH and DCIS samples, however, differed significantly (P < .0001).
  
  
  CONCLUSIONS
  DCIS lesions contain levels of genomic instability that are characteristic of advanced invasive tumors, and this suggests that the biology of a developing carcinoma may already be predetermined by the in situ stage. Observations that levels of AI in ADH lesions are similar to those in disease-free tissues provide a genomic rationale for why prevention strategies at the ADH level are successful and why cases with ADH involving surgical margins do not require further resection.
authors.affiliation: Clinical Breast Care Project, Windber Research Institute, 620 Seventh Street, Windber, PA 15963, USA. r.ellsworth@wriwindber.org
authors.forename: Rachel E
authors.initials: RE
authors.lastname: Ellsworth
authors.forename: Darrell L
authors.initials: DL
authors.lastname: Ellsworth
authors.forename: Brenda
authors.initials: B
authors.lastname: Deyarmin
authors.forename: Laurel R
authors.initials: LR
authors.lastname: Hoffman
authors.forename: Brad
authors.initials: B
authors.lastname: Love
authors.forename: Jeffrey A
authors.initials: JA
authors.lastname: Hooke
authors.forename: Craig D
authors.initials: CD
authors.lastname: Shriver
mesh_terms: D022981:Allelic Imbalance; D001940:Breast / Q000378:metabolism / Q000473:pathology*; D001943:Breast Neoplasms / Q000235:genetics* / Q000473:pathology*; D018270:Carcinoma, Ductal, Breast / Q000235:genetics; D002285:Carcinoma, Intraductal, Noninfiltrating / Q000235:genetics*; D018275:Carcinoma, Lobular / Q000235:genetics; D018450:Disease Progression; D042822:Genomic Instability; D006801:Humans; D006965:Hyperplasia; D007150:Immunohistochemistry; D018895:Microsatellite Repeats