Luminal A and luminal B (HER2 negative) subtypes of breast cancer consist of a mixture of tumors with different genotype

Abstract

BackgroundThe 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.MethodsInvasive 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.ResultsThe 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.ConclusionsIt 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.

Association of Immunohistochemically Defined Molecular Subtypes with Clinical Response to Presurgical Chemotherapy in Patients with Advanced Breast Cancer

“…The only patient among the Luminal group exhibiting cCR had the Luminal B HER2 negative subtype. This heterogeneity of response to chemotherapy is in consistence with the genomic heterogeneity reported for the Luminal A and Luminal B types of breast cancers (Yanagawa et al, 2012). Lack of efficacy of neoadjuvant chemotherapy in patients with ER positive tumors and Luminal A tumors is well documented (Carey et al, 2007;Colleoni et al, 2009;Lv et al, 2011) and the use of adjuvant chemotherapy has been debated in the Luminal A subclass of patients with early breast cancer (Coates et al, 2012) and IX trials found no benefit of adding chemotherapy in patients with ER positive disease (Aebi et al, 2011;Karlsson et al, 2011).…”

The role of ultrasonographic findings to predict molecular subtype, histologic grade, and hormone receptor status of breast cancer

“…Hence, suitable classification is needed for appropriate individual management (9-11). Currently due to the inadequate prognostic power and predictive accuracy of existing classifications, a modified classification according to molecular characteristics of breast cancer was defined by the 13 th St. Gallen Breast Cancer Conference to categorize breast cancers into molecular subtypes (1). Despite the lack of a complete overlap among molecular classes and their immunohistochemical status, the St. the patients in our study had luminal A and B molecular subtypes (78%) and only 13% had triple-negative breast cancer.…”

“…Molecular subtypes were defined as follows: Luminal A: ER+, PR+, HER2-, and low Ki-67 index; luminal B (HER2-): ER+, PR+ or PR-, HER2-, and high Ki-67 index; luminal B (HER2+): ER+, PR+, HER2+; HER2: ER-, PR-, HER2+; and triple-negative: ER-, PR-, HER2-. In our study, the Ki-67 index was scored as high when 14% or more of the tumor cells were immunohistostained in accordance with the St. Gallen International Expert Consensus guidelines (1). Immunohistochemistry results were taken from the reports and recorded.…”

Identification of Genes Differentially Associated with Triple Negative Breast Cancers

“…The number of molecular designations for the breast cancer subtypes have increased recently, nonetheless the core groupings continue to be luminal A, luminal B, HER2+, Basal-like breast cancer (BLBC) and triple negative breast cancer (TNBC) (1,2). Luminal A are characterized as positive for estrogen receptor gene (ER+) and progesterone receptor (PR+), and human epidermal growth factor receptor 2negative (HER2-).…”