title: Molecular subtypes of breast cancer emerging in young women in Taiwan: evidence for more than just westernization as a reason for the disease in Asia.
abstract: BACKGROUND
  In the past two decades, the incidence of breast cancer in young Taiwanese females has been rapidly increasing, approaching the risk level of western countries. As a first step to investigate the possible etiology, we examined the molecular subtypes of female breast cancer in Taiwan.
  
  
  METHODS
  This study included 1,028 consecutive patients with breast cancer diagnosed in National Taiwan University Hospital between 2004 and 2006. Estrogen receptor (ER), progesterone receptor (PR), human epidermal growth factor receptor-2, cytokeratin 5/6, and epidermal growth factor receptor expression and/or gene amplification were analyzed.
  
  
  RESULTS
  Younger (<or=50 years) breast cancer patients had a higher prevalence of luminal A (67% versus 57%; P < 0.001) and a lower prevalence of basal-like subtype (9% versus 17%; P < 0.001) compared with older (>50 years) patients. The higher prevalence of luminal A subtype was mainly attributed to a higher ER (75% versus 63%; P < 0.001) and PR (47% versus 33%; P < 0.001) expression rate in younger patients than older patients. Tumors with histologic grade 3 were less prevalent in younger patients than in older patients (23% versus 30%; P = 0.01). For very young (<35 years) patients, the molecular subtype distribution, ER and/or PR expression rate, and histologic grade were not significantly different from those of less young (35-50 years) patients.
  
  
  CONCLUSIONS
  Young breast cancer patients in Taiwan are characterized by a high prevalence of luminal A subtype and low prevalence of histologic grade 3 tumor and/or basal-like subtype. These features are distinct from young breast cancer patients in western countries.
authors.affiliation: Department of Oncology, National Taiwan University Hospital, Taipei, Taiwan.
authors.forename: Ching-Hung
authors.initials: CH
authors.lastname: Lin
authors.forename: Jau-Yu
authors.initials: JY
authors.lastname: Liau
authors.forename: Yen-Shen
authors.initials: YS
authors.lastname: Lu
authors.forename: Chiun-Sheng
authors.initials: CS
authors.lastname: Huang
authors.forename: Wei-Chung
authors.initials: WC
authors.lastname: Lee
authors.forename: Kuan-Ting
authors.initials: KT
authors.lastname: Kuo
authors.forename: Ying-Chun
authors.initials: YC
authors.lastname: Shen
authors.forename: Sung-Hsin
authors.initials: SH
authors.lastname: Kuo
authors.forename: Chieh
authors.initials: C
authors.lastname: Lan
authors.forename: Jacqueline Ming
authors.initials: JM
authors.lastname: Liu
authors.forename: Wun-Hon
authors.initials: WH
authors.lastname: Kuo
authors.forename: King-Jen
authors.initials: KJ
authors.lastname: Chang
authors.forename: Ann-Lii
authors.initials: AL
authors.lastname: Cheng
mesh_terms: D017677:Age Distribution; D000367:Age Factors; D014408:Biomarkers, Tumor / Q000032:analysis*; D001943:Breast Neoplasms / Q000453:epidemiology* / Q000235:genetics* / Q000473:pathology*; D066246:ErbB Receptors / Q000096:biosynthesis / Q000235:genetics; D005260:Female; D015870:Gene Expression; D006801:Humans; D007150:Immunohistochemistry; D017404:In Situ Hybridization, Fluorescence; D015994:Incidence; D053555:Keratin-5 / Q000096:biosynthesis / Q000235:genetics; D053553:Keratin-6 / Q000096:biosynthesis / Q000235:genetics; D009367:Neoplasm Staging; D018719:Erb-b2 Receptor Tyrosine Kinases / Q000096:biosynthesis / Q000235:genetics; D011960:Receptors, Estrogen / Q000096:biosynthesis / Q000235:genetics; D011980:Receptors, Progesterone / Q000096:biosynthesis / Q000235:genetics; D013624:Taiwan
chemical_list: D014408:Biomarkers, Tumor; D066246:ErbB Receptors; D053555:Keratin-5; D053553:Keratin-6; D018719:Erb-b2 Receptor Tyrosine Kinases; D011960:Receptors, Estrogen; D011980:Receptors, Progesterone