Molecular subtypes of breast cancer

There are many different types of breast cancer. Some are slow growing and "well behaved" while others are much more aggressive. Traditional pathology reporting describes the cancer by the appearance of the cells under the microscope as ductal / lobular or special type. This appearance does not however reliably predict the behaviour of the tumour.  Recent advances in pathology have allowed a much more detailed analysis of the structure of the cancer cells at a molecular level.

Using these methods researchers have identified four main groups of breast cancer.


Molecular features


Luminal A

ER+, +/-PR+,HER2 - , lowK67


Luminal B

ER+, +/-PR+, HER2+(or HER2- with high Ki67)



ER-, PR-, HER2-,cytokeratin5/6+


HER 2 type

ER-,PR-, HER2+


Normal breast like

Cancers that cannot be satisfactorily classified in 4 groups above



Luminal A

The cancer cells look similar to the ductal cells on the inside lining of the breast ducts. (the lumen of the duct is the space inside and the luminal cells are the layer of cells closest to this surface)These tumours appear to have the best prognosis. Treatment can include hormonal manipulation as they are receptor positive.

Luminal B

These tumours have a poorer prognosis and tend to occur in younger women.

Basal like tumours

These tumours have cells that look more like the cells on the outer layer of the duct lining. Most contain p53 mutations. Most basal tumours are triple negative which means that the cells do not express the oestrogen, progesterone or HER2 receptors. Treatment options are limited as we cannot use anti-oestrogen drugs like Tamoxifen or the Aromatase Inhibitors. Herceptin is also of no use in this situation. The medical oncologists will plan systemic treatment using chemotherapy drugs. There is a lot of research interest in newer drugs for this group of cancers.

PARP inhibitors

Targets for therapy - EGF receptor ,aB-crystallin and cyclin E.

HER2 type

These have a poorer prognosis and are associated with higher risk of early recurrence and metastases.


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