Molecular classification of breast cancer

Molecular types

Receptor status was traditionally considered by reviewing each individual receptor (ER, PR, HER2) in turn, but newer approaches look at these together, along with the tumor grade, to categorize breast cancer into several conceptual molecular classes that have different prognoses and may have different responses to specific therapies.

DNA microarrays have assisted this approach, as discussed in the following section. Proposed molecular subtypes include:

 Basal-like: ER-, PR- and HER2-; also called triple negative breast cancer (TNBC) / Most BRCA1 breast cancers are basal-like TNBC.
 Luminal A: ER+ and low grade
 Luminal B: ER+ but often high grade
 Luminal ER-/AR+: (overlapping with apocrine and so called molecular apocrine) - recently identified androgen responsive subtype which may respond to antihormonal treatment with bicalutamide
 ERBB2/HER2+: has amplified HER2/neu
 Normal breast-like
 Claudin-low: a more recently described class; often triple-negative, but distinct in that there is low expression of cell-cell junction proteins including E-cadherin and frequently there is infiltration with lymphocytes.

Commercial tests

 OncotypeDx (Genomic Health)
 Prosigna (Nanostring)
 MammaPrint (Agendia)
 Theros
 MapQuantDx