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Molecular classification of breast cancer

Monday 15 September 2014

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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