Understanding the Differences Between Breast Cancer Subtypes

October 8, 2019

Breast cancer is the most common cancer in women around the world, with more than 2 million new cases diagnosed in 2018.1 But not all breast cancers are the same. Breast cancer can behave in different ways depending on its anatomical situation, presence or absence of biological markers like hormone receptors and the HER2 oncogene, the level of spread and the treatment received.2

Understanding what type of breast cancer a patient has and whether or not the growth of those cancer cells are being fueled by hormones has traditionally helped doctors determine what course of treatment to recommend.

Molecular Subtypes

Thanks to advances in technology and the ability to analyze large sets of data, researchers have been able to dig deeper into understanding the genes of individual cells. By describing certain characteristics of different cells – such as whether or not cancers are fueled by hormones (hormone receptor positive or negative) and whether the cells contain HER2 proteins - researchers have identified molecular subtypes that exist within these broader breast cancer categories.

3-D illustration of a breast cancer cell

The five molecular subtypes of breast cancer are luminal A, luminal B, triple-negative/basal-like, HER2 enriched and normal like.3 Luminal A is the most common breast cancer subtype, accounting for as many as 60 percent of all breast cancers.4 Learn more about these subtypes below:

  • Luminal A breast cancer cells are hormone-receptor positive, HER2 negative and have low levels of a key protein called Ki-67 that helps control how fast the cancer grows.
  • Luminal B breast cancer cells are hormone-receptor positive, and either HER2 positive or HER2 negative with high levels of Ki-67.
  • Triple-negative/basal-like breast cancer cells are hormone-receptor negative and HER2 negative.
  • HER2 enriched breast cancer cells are hormone-receptive negative and HER2 positive.
  • Normal like breast cancer cells are similar in profile to luminal A cells but with a slightly different prognosis5

Targeting Treatments

Why is it important for healthcare professionals to know the molecular subtype of breast cancers? It’s because each subtype tells us different things about the characteristics of a cancer cell and how it will react to different treatments.3

Breast cancer treatments can include surgery, radiation therapy, chemotherapy, hormone therapy, targeted therapy and immunotherapy. Treatment that works for one kind of breast cancer may not work for another.

By understanding a cancer cell’s molecular subtype, doctors can make better decisions about which treatment is appropriate for each patient, saving money for the healthcare system overall and resulting in patients avoiding side effects from unnecessary treatments.6

Mylan is a Champion for Breast Cancer Care

Mylan has one of the broadest and most diverse medicine portfolios, including treatment options for breast cancer. Our goal is to promote better health for a better world so that all patients around the globe have access to the medicine they need.

1 World Cancer Research Fund. (2018). Breast cancer statistics. [online] Available at: https://www.wcrf.org/dietandcancer/cancer-trends/breast-cancer-statistics  Accessed September 11, 2019.

2 www.nationalbreastcancer.org. (2019). Breast Cancer Types :: The National Breast Cancer Foundation. [online] Available at: https://www.nationalbreastcancer.org/types-of-breast-cancer Accessed September 11,  2019.

3 Xiaofeng Dai, B. (2019). Breast cancer intrinsic subtype classification, clinical use and future trends. [online] PubMed Central (PMC). Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4656721/ Accessed September 11,  2019.

4 Yersal, O. (2014). Biological subtypes of breast cancer: Prognostic and therapeutic implications. World Journal of Clinical Oncology, [online] 5(3), p.412. Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4127612/  Accessed September 11, 2019.

5 Breastcancer.org. (2019). Molecular Subtypes of Breast Cancer. [online] Available at: https://www.breastcancer.org/symptoms/types/molecular-subtypes  Accessed September 12, 2019.

6 Accc-cancer.org. (2019). [online] Available at: https://www.accc-cancer.org/docs/documents/oncology-issues/articles/so15/so15-how-molecular-subtyping-is-changing-our-understanding-of-breast-cancer.pdf?sfvrsn=e7898ce0_9  Accessed September 12, 2019.