Breast Cancer 101

Breast Cancer Genetic Types

Breast Cancer 101 Breast Cancer Genetic Types

Breast Cancer Genetic Types Information

In recent years, the medical community's understanding of the different gene mutations in breast cancer has grown significantly due to advancements in gene detection technology and our understanding of the human genome. This has ushered in a new era of breast cancer classification based on gene analysis techniques called microarray analysis. The results of this analysis have determined the existence of four distinct types of breast cancer:

  • Luminal A.
  • Luminal B.
  • Basal cell (also referred to as triple-negative).
  • HER2-positive.

If you have been diagnosed with breast cancer, your cancer will be categorized into one of the four types of breast cancer based on the:

  • Appearance of cancerous tissue examined under a microscope.
  • Location where the cancer began, either in the duct or the lobule.
  • Presence or absence of estrogen and progesterone hormone receptors on cancer cells.
  • Possible production of a cancer gene called the Human Epidermal Growth Factor Receptor-2 (HER2) oncogene.

Each of these types of breast cancer presents different growth patterns, varying abilities to spread beyond the breast, and distinct disease outcomes. Learning your breast cancer type will help you make informed choices about the best treatment options for you.

Luminal A

Luminal A breast cancers are slow-growing and low-grade, with cure rates that exceed 90 percent. Representing approximately 35 percent of all breast cancer cases, Luminal A breast cancers are often discovered through screening mammography.

Luminal A breast cancer cells resemble normal breast tissue cells and tend to remain localized without spreading into the lymph system or bloodstream. Due to their slow growth and low likelihood of spreading, there is a risk of overtreatment for Luminal A breast cancers.

Typically, Luminal A breast cancers can be cured without chemotherapy, using limited surgery alone or in combination with radiation therapy. However, if left untreated, there is a possibility that Luminal A cancers can develop into Luminal B cancers.

Luminal B

Luminal B breast cancers exhibit more aggressive and rapid growth compared to Luminal A types. They are also more likely to spread beyond the breast to lymph nodes and blood vessels. Luminal B breast cancers account for approximately 30 percent of all breast cancer cases.

Contrasting with Luminal A cancers, which tend to be situated in a specific site, Luminal B cancers can manifest in multiple sites within a particular region of the breast, with normal breast tissue existing in between. In these instances, mammography often underestimates the size of primary cancers and fails to detect secondary cancers. Magnetic resonance imaging (MRI) can help to more accurately measure and detect Luminal B cancers.

Treatments for Luminal B breast cancers may include limited surgery, mastectomy, radiation therapy, and chemotherapy. However, recommended treatment options available to each woman will vary based on a range of personal factors regarding her disease and her risk factors. This individualized approach ensures the most appropriate and effective treatment plan is put into place.

Triple-Negative and Basal-Type

Basal-type cancers, of which approximately 90 percent are truly triple-negative, make up roughly 15-20 percent of all breast cancer cases. The term "triple-negative" is commonly used within the medical and patient communities to describe cancers that lack hormone receptors on the cancer cells and do not overproduce HER2. Among basal-type cancers, the remaining 10 percent that are not truly triple-negative do have some degree of hormone positivity.

Triple-negative cancers are characterized by their aggressive growth and rapid progression. They do not respond to hormonal therapy. About 90 percent of women with a BRCA1 gene mutation who develop breast cancer have the triple-negative type. Triple-negative breast cancers are more prevalent among younger women and African-American women.

Treatment for triple-negative breast cancers typically involves a combination of surgery, radiation therapy, and chemotherapy. Although the prognosis for triple-negative cancers has traditionally been relatively poor, it is improving as targeted therapies are being developed and investigated.


HER2-positive cancers, which account for approximately 20 percent of all breast cancer cases, overproduce the HER2 oncogene. These cancers are aggressive, grow rapidly, can spread easily, and often result in recurrence.

Historically, the prognosis for HER2-positive cancers has been fairly poor. However, advancements in our understanding of how HER2-positive cancer cells function have led to the development of targeted treatments that disrupt the internal pathways of HER2-positive cells, causing them to die. For this reason, accurate diagnosis of HER2-positive breast cancers is critical to ensure the most appropriate and effective treatment options



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