title: Geographic differences in the distribution of molecular subtypes of breast cancer in Brazil.
abstract: BACKGROUND
  To compare the distribution of the intrinsic molecular subtypes of breast cancer based on immunohistochemical profile in the five major geographic regions of Brazil, a country of continental dimension, with a wide racial variation of people.
  
  
  METHODS
  The study was retrospective observational. We classified 5,687 invasive breast cancers by molecular subtype based on immunohistochemical expression of estrogen-receptor (ER), progesterone-receptor (PR), human epidermal growth factor receptor 2 (HER2), and Ki-67 proliferation index. Cases were classified as luminal A (ER and/or PR positive and HER2 negative, Ki-67 < 14%), luminal B (ER and/or PR positive, HER2 negative, and Ki-67 > 14%), triple-positive (ER and/or PR positive and HER2 positive), HER2-enriched (ER and PR negative, and HER2- positive), and triple-negative (TN) (ER negative, PR negative, and HER2- negative). Comparisons of the ages of patients and molecular subtypes between different geographic regions were performed.
  
  
  RESULTS
  South and Southeast regions with a higher percentage of European ancestry and higher socioeconomic status presented with the highest proportion of luminal tumors. The North region presented with more aggressive subtypes (HER2-enriched and triple-negative), while the Central-West region predominated triple-positive carcinomas. The Northeast--a region with a high African influence--presented intermediate frequency of the different molecular subtypes. The differences persisted in subgroups of patients under and over 50 years.
  
  
  CONCLUSIONS
  The geographic regions differ according to the distribution of molecular subtypes of breast cancer. However, other differences, beside those related to African ancestry, such as socioeconomic, climatic, nutritional, and geographic, have to be considered to explain our results. The knowledge of the differences in breast cancer characteristics among the geographic regions may help to organize healthcare programs in large countries like Brazil with diverse economic and race composition among different geographic regions.
authors.affiliation: Department of Pathology, Faculdade de Medicina da Universidade de São Paulo, Av, Dr, Arnaldo, 455 - room 1149, São Paulo, SP 01246-903, Brazil. filomena@usp.br.
authors.forename: Filomena M
authors.initials: FM
authors.lastname: Carvalho
authors.forename: Lívia M
authors.initials: LM
authors.lastname: Bacchi
authors.forename: Kátia M
authors.initials: KM
authors.lastname: Pincerato
authors.forename: Matt
authors.initials: M
authors.lastname: Van de Rijn
authors.forename: Carlos E
authors.initials: CE
authors.lastname: Bacchi
mesh_terms: D000293:Adolescent; D000328:Adult; D000367:Age Factors; D000368:Aged; D000369:Aged, 80 and over; D014408:Biomarkers, Tumor / Q000378:metabolism*; D044383:Black People / Q000706:statistics & numerical data; D001938:Brazil / Q000453:epidemiology; D001943:Breast Neoplasms / Q000453:epidemiology* / Q000378:metabolism; D002277:Carcinoma / Q000453:epidemiology*; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D019394:Ki-67 Antigen / Q000378:metabolism; D008875:Middle Aged; D017720:Molecular Epidemiology; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000378:metabolism; D011960:Receptors, Estrogen / Q000378:metabolism; D011980:Receptors, Progesterone / Q000378:metabolism; D012189:Retrospective Studies; D064726:Triple Negative Breast Neoplasms / Q000453:epidemiology* / Q000378:metabolism; D044465:White People / Q000706:statistics & numerical data; D055815:Young Adult
chemical_list: D014408:Biomarkers, Tumor; D019394:Ki-67 Antigen; D018719:Erb-b2 Receptor Tyrosine Kinases; D011960:Receptors, Estrogen; D011980:Receptors, Progesterone