Major Subtypes of Human Breast Cancer
| Molecular subtype | Gene expression features | Clinical features | Treatment and prognosis |
| Luminal | Elevated expression of hormone receptors and associated genes (luminal A > luminal B) | ∼65% of invasive breast cancers are ER- or PR-positive | Respond to endocrine therapy (responses to tamoxifen and aromatase inhibitors may differ in luminal A and B cancers) |
| Luminal B cancers tend to be of higher histologic grade than luminal A cancers | Variable response to chemotherapy (greater in luminal B cancers than in luminal A cancers) | ||
| Some overexpress HER2 (luminal B) | Prognosis is better for luminal A cancers than for luminal B cancers | ||
| HER2 | Elevated expression of HER2 and other genes in amplicon | ∼15% of invasive breast cancers are ER- or PR-negative | Respond to trastuzumab (Herceptin) |
| Respond to anthracycline-based chemotherapy | |||
| Low expression of ER, PR, and associated genes | High probability of being high-grade and node-positive | Prognosis is typically poor | |
| Basallike | Elevated expression of basal epithelial genes and basal cytokeratins | ∼15% of invasive breast cancers | No response to endocrine therapy or trastuzumab (Herceptin) |
| Low expression of ER, PR, and associated genes | Most are ER-, PR-, and HER2-negative (TNBC) | Appear to be sensitive to platinum-based chemotherapy and polyadenosine ribose polymerase inhibitors | |
| Low expression of HER2 | BRCA1 dysfunction (germ line, sporadic) | Prognosis is typically poor (but not uniformly poor) | |
| Particularly common in African American women |
Adapted with permission of (10).