title: Luminal A and luminal B (HER2 negative) subtypes of breast cancer consist of a mixture of tumors with different genotype.
abstract: BACKGROUND
  The St Gallen International Expert Consensus 2011 has proposed a new classification system for breast cancer. The purpose of this study was to elucidate the relationship between the breast cancer subtypes determined by the new classification system and genomic characteristics.
  
  
  METHODS
  Invasive breast cancers (n = 363) were immunohistochemically classified as follows: 111 (30.6%) as luminal A, 95 (26.2%) as luminal B (HER2 negative), 69 (19.0%) as luminal B (HER2 positive), 41 (11.3%) as HER2, and 47 (12.9%) as basal-like subtypes.
  
  
  RESULTS
  The high expression of Ki-67 antigen was detected in 236 tumors; no cases of luminal A subtype showed high expression of the Ki-67 antigen, but more than 85% of tumors of the other subtypes showed high expression. In addition, DNA ploidy and chromosomal instability (CIN) were assessed using imaging cytometry and FISH, respectively. In this series, 336 (92.6%) tumors consisted of 129 diploid/CIN- and 207 aneuploid/CIN + tumors. Diploid/CIN- and aneuploid/CIN+ features were detected in 64.9% and 27.9% of luminal A, 41.1% and 49.5% of luminal B (HER2-), 11.6% and 81.2% of luminal B (HER2+), 4.9% and 90.2% of HER2, and 17.0% and 76.6% of basal-like subtypes, respectively. Unlike the luminal B (HER2+), HER2 and basal-like subtypes, the luminal A and luminal B (HER2-) subtypes were heterogeneous in terms of DNA ploidy and CIN.
  
  
  CONCLUSIONS
  It is reasonable to propose that the luminal A and luminal B (HER2-) subtypes should be further divided into two subgroups, diploid/CIN- and aneuploid/CIN+, based on their underlying genomic status.
authors: Departments of Pathology, Yamaguchi University Graduate School of Medicine, Ube-shi 755-8505, Japan.
authors: Masumi
authors: M
authors: Yanagawa
authors: Kenzo
authors: K
authors: Ikemot
authors: Shigeto
authors: S
authors: Kawauchi
authors: Tomoko
authors: T
authors: Furuya
authors: Shigeru
authors: S
authors: Yamamoto
authors: Masaaki
authors: M
authors: Oka
authors: Atunori
authors: A
authors: Oga
authors: Yukiko
authors: Y
authors: Nagashima
authors: Kohsuke
authors: K
authors: Sasaki
mesh_terms: D000328:Adult; D000368:Aged; D000782:Aneuploidy; D001943:Breast Neoplasms / Q000145:classification* / Q000235:genetics* / Q000473:pathology; D049109:Cell Proliferation; D043171:Chromosomal Instability / Q000235:genetics; D004273:DNA, Neoplasm / Q000235:genetics; D005260:Female; D015894:Genome, Human / Q000235:genetics; D005838:Genotype; D006801:Humans; D007150:Immunohistochemistry; D017404:In Situ Hybridization, Fluorescence; D019394:Ki-67 Antigen / Q000378:metabolism; D008875:Middle Aged; D060787:Neoplasm Grading; D009363:Neoplasm Proteins / Q000378:metabolism; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000378:metabolism*
chemical_list: D004273:DNA, Neoplasm; D019394:Ki-67 Antigen; D009363:Neoplasm Proteins; D018719:Erb-b2 Receptor Tyrosine Kinases