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.
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.
Lin
Ching-Hung
CH
Department of Oncology, National Taiwan University Hospital, Taipei, Taiwan.
Liau
Jau-Yu
JY
Lu
Yen-Shen
YS
Huang
Chiun-Sheng
CS
Lee
Wei-Chung
WC
Kuo
Kuan-Ting
KT
Shen
Ying-Chun
YC
Kuo
Sung-Hsin
SH
Lan
Chieh
C
Liu
Jacqueline Ming
JM
Kuo
Wun-Hon
WH
Chang
King-Jen
KJ
Cheng
Ann-Lii
AL
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
D014408:Biomarkers, Tumor; D066246:ErbB Receptors; D053555:Keratin-5; D053553:Keratin-6; D018719:Erb-b2 Receptor Tyrosine Kinases; D011960:Receptors, Estrogen; D011980:Receptors, Progesterone