title: Breast cancer subtype distribution is different in normal weight, overweight, and obese women.
abstract: OBJECTIVE
  Obesity is associated with tumor promoting pathways related to insulin resistance and chronic low-grade inflammation which have been linked to various disease states, including cancer. Many studies have focused on the relationship between obesity and increased estrogen production, which contributes to the pathogenesis of estrogen receptor-positive breast cancers. The link between obesity and other breast cancer subtypes, such as triple-negative breast cancer (TNBC) and Her2/neu+ (Her2+) breast cancer, is less clear. We hypothesize that obesity may be associated with the pathogenesis of specific breast cancer subtypes resulting in a different subtype distribution than normal weight women.
  
  
  METHODS
  A single-institution, retrospective analysis of tumor characteristics of 848 patients diagnosed with primary operable breast cancer between 2000 and 2013 was performed to evaluate the association between BMI and clinical outcome. Patients were grouped based on their BMI at time of diagnosis stratified into three subgroups: normal weight (BMI = 18-24.9), overweight (BMI = 25-29.9), and obese (BMI > 30). The distribution of breast cancer subtypes across the three BMI subgroups was compared.
  
  
  RESULTS
  Obese and overweight women were more likely to present with TNBC and normal weight women with Her2+ breast cancer (p = 0.008).
  
  
  CONCLUSIONS
  We demonstrated, for the first time, that breast cancer subtype distribution varied significantly according to BMI status. Our results suggested that obesity might activate molecular pathways other than the well-known obesity/estrogen circuit in the pathogenesis of breast cancer. Future studies are needed to understand the molecular mechanisms that drive the variation in subtype distribution across BMI subgroups.
authors.affiliation: Department of Surgery, Perelman School of Medicine, University of Pennsylvania, 3400 Civic Center Boulevard, 10th Floor South, Philadelphia, PA, 19104, USA.
authors.forename: Victoria
authors.initials: V
authors.lastname: Gershuni
authors.affiliation: Department of Surgery, Perelman School of Medicine, University of Pennsylvania, 3400 Civic Center Boulevard, 10th Floor South, Philadelphia, PA, 19104, USA.|Internal Medicine Residency Program, Department of Medicine, Eisenhower Medical Center, Rancho Mirage, CA, USA.
authors.forename: Yun R
authors.initials: YR
authors.lastname: Li
authors.affiliation: Department of Surgery, Perelman School of Medicine, University of Pennsylvania, 3400 Civic Center Boulevard, 10th Floor South, Philadelphia, PA, 19104, USA.
authors.forename: Austin D
authors.initials: AD
authors.lastname: Williams
authors.affiliation: Department of Surgery, Perelman School of Medicine, University of Pennsylvania, 3400 Civic Center Boulevard, 10th Floor South, Philadelphia, PA, 19104, USA.
authors.forename: Alycia
authors.initials: A
authors.lastname: So
authors.affiliation: Department of Surgery, Perelman School of Medicine, University of Pennsylvania, 3400 Civic Center Boulevard, 10th Floor South, Philadelphia, PA, 19104, USA.
authors.forename: Laura
authors.initials: L
authors.lastname: Steel
authors.affiliation: Department of Surgery, Perelman School of Medicine, University of Pennsylvania, 3400 Civic Center Boulevard, 10th Floor South, Philadelphia, PA, 19104, USA.
authors.forename: Elena
authors.initials: E
authors.lastname: Carrigan
authors.affiliation: Department of Surgery, Perelman School of Medicine, University of Pennsylvania, 3400 Civic Center Boulevard, 10th Floor South, Philadelphia, PA, 19104, USA. julia.tchou@uphs.upenn.edu.
authors.forename: Julia
authors.initials: J
authors.lastname: Tchou
mesh_terms: D000368:Aged; D015992:Body Mass Index; D018572:Disease-Free Survival; D006801:Humans; D008207:Lymphatic Metastasis; D008875:Middle Aged; D009765:Obesity / Q000378:metabolism / Q000401:mortality / Q000473:pathology*; D016016:Proportional Hazards Models; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000378:metabolism; D012189:Retrospective Studies; D016896:Treatment Outcome; D064726:Triple Negative Breast Neoplasms / Q000378:metabolism / Q000401:mortality / Q000473:pathology*
chemical_list: D018719:Erb-b2 Receptor Tyrosine Kinases; C508053:ERBB2 protein, human
keywords: Breast cancer; Breast cancer subtype; Her2+ breast cancer; Obesity; Overweight; TNBC