Triple-negative, basal-like, and quintuple-negative breast cancers: better prediction model for survival

Using tissue microarray-based immunohistochemical analysis, we categorized 951 primary breast cancers into four or five subtypes according to the expression of ER, PR, HER2, and basal markers (CK5/6, EGFR).The results of this study showed that both TNBCs and BLBCs were associated with high histological and/or nuclear grades. When the TNBCs are divided into two subtypes by the presence of basal markers, the clinicopathologic characteristics of TNBCs were mainly maintained in the BLBCs. The 5-subgrouping was the better prediction model for both disease free and overall survival in breast cancers than the 4-subgrouping. After multivariate analysis of TNBCs, the BLBCs did not have a worse prognosis than the QNBC/5NPs. Interestingly, the patients with BLBCs showed significant adjuvant chemotherapy benefit. In addition, QNBC/5NPs comprised about 6~8% of breast cancers in publicly available breast cancer datasetsThe QNBC/5NP subtype is a worse prognostic subgroup of TNBCs, especially in higher stage and this result may be related to adjuvant chemotherapy benefit of BLBCs, calling for caution in the identification of subgroups of patients for therapeutic classification.Breast cancer is a heterogeneous disease, and basal-like breast cancers (BLBCs) have attracted particular attention because they have been shown to have shorter survival compared to the other subtypes [1,2]. With the practical difficulties of gene-expression profiling as a routine diagnostic tool, immunohistochemical surrogate panels have been introduced to identify BLBCs that are 'triple-negative breast cancers' (TNBCs) (estrogen receptor (ER)-negative, progesterone receptor (PR)-negative, HER2 not overexpressed) [2,3]. The immunohistochemical panel that is considered to be the gold standard in the identification of BLBCs was proposed by Nielsen et al., in which BLBCs are defined as breast cancers expressing neither ER/PR nor HER2 and expressing CK5/6 and/or EGFR [2]. Both TNBCs and BLBCs have attracted clin