title: Menopausal hormone therapy and risk of clinical breast cancer subtypes.
abstract: BACKGROUND
  Breast cancer is a heterogeneous disease with subtypes that may vary in their etiologies. Menopausal hormone therapy has been associated more strongly with lobular and tubular than ductal histologic types and with tumors that are smaller, hormone receptor-positive, and of lower grade. At the same time, correlations have been observed between histology and clinical characteristics. To identify those tumor subtypes most strongly associated with hormone therapy use, it is necessary to disentangle these interrelationships.
  
  
  METHODS
  Based on 3,464 postmenopausal breast cancer cases and 6,657 controls from the population-based Mammary carcinoma Risk factor Investigation study, we used polytomous logistic regression to evaluate associations between hormone therapy use and risk of invasive breast cancer subtypes. We assessed variations in risk for selected tumor characteristics among histologic and hormone receptor subtypes, both overall and for specific hormone therapy regimens.
  
  
  RESULTS
  Lobular and mixed types showed less variation by prognostic factors than did ductal tumors. Current hormone therapy use had the strongest associations with prognostic variables in estrogen receptor (ER)-positive and/or progesterone receptor (PR)-positive ductal tumors and in lobular tumors regardless of ER/PR status, with little effect on ER/PR-negative ductal tumors. The observed associations varied minimally by hormone therapy type or regimen.
  
  
  CONCLUSIONS
  Current hormone therapy use was associated with more favorable breast cancer characteristics for ductal tumors but had less effect on prognostic characteristics in women with lobular tumors. Both histologic type and estrogen receptor/progesterone receptor status seem to be important in explaining the role of hormone therapy in the etiology of breast cancer subtypes.
authors.affiliation: Division of Cancer Epidemiology, German Cancer Research Center, Heidelberg, Germany. t.slanger@hotmail.com
authors.forename: Tracy E
authors.initials: TE
authors.lastname: Slanger
authors.forename: Jenny C
authors.initials: JC
authors.lastname: Chang-Claude
authors.forename: Nadia
authors.initials: N
authors.lastname: Obi
authors.forename: Silke
authors.initials: S
authors.lastname: Kropp
authors.forename: Jürgen
authors.initials: J
authors.lastname: Berger
authors.forename: Eik
authors.initials: E
authors.lastname: Vettorazzi
authors.forename: Wilhelm
authors.initials: W
authors.lastname: Braendle
authors.forename: Gunter
authors.initials: G
authors.lastname: Bastert
authors.forename: Stefan
authors.initials: S
authors.lastname: Hentschel
authors.forename: Dieter
authors.initials: D
authors.lastname: Flesch-Janys