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Breast Cancer Basics

Types & Sub-Types


Sub-Types of Breast Cancer

Hormone receptor-positive (HR+) breast cancer refers to cancers in which the cells have receptors (proteins located inside the cell) that can receive signals from hormones that drive cell growth. Breast cancer can be estrogen-receptor positive (ER+) if it has receptors for estrogen, or progesterone-receptor positive (PR+) if it has receptors for progesterone.  It is helpful to know your hormone status as it can help you and your health care team decide if hormonal therapies and other treatments would be of benefit to you.

HER2-positive breast cancers are known for the overexpression of the human epidermal growth factor receptor 2 (HER2) protein. HER2 proteins are receptors found on the surface of breast cells that are overexpressed in some breast cancers. In healthy cells, HER2 receptors are involved in controlling normal cell growth, division and repair. In HER2-positive breast cancers, the cells overproduce the HER2 protein, which can result in the uncontrolled division and growth of cells. An estimated 20 percent of breast cancers are believed to be HER2-positive.  These cancers are often treated with treatments targeted to the HER2 receptor, which has greatly improved the prognosis of this disease.

Triple-negative breast cancer (TNBC) refers to cancers whose growth is not driven by the hormones estrogen or progesterone or by the overexpression of HER2 (human epidermal growth factor receptor) proteins. Targeted therapies developed for hormone receptor-positive and HER2-positive breast cancers are often ineffective against triple-negative breast cancers. Chemotherapy, surgery and radiation are the most effective treatments currently available for TNBC.

Breast cancer has also been divided into five major molecular subtypes:  luminal A, luminal B, HER2-enriched, basal-like, and normal. While, receptor status is the most important feature used for decision-making in clinical practice, standard pathologic assessments often include characteristics that can indicate the molecular subtype as well.

Luminal A cancers typically tend to be HR+ and HER2-negative, with low nuclear grade.  Luminal B cancers are also HR+, but may be higher grade and may be HER2-positive.  HER2-positive breast cancers tend to be strongly HER2-positive, and HR-.  Basal like cancers are often triple negative, however these terms are not entirely interchangeable.  Different types of breast cancer receive different types of treatment.  Understanding your breast cancer type and sub-type can better prepare you for a discussion with your doctor.

Know Your Type

Are you metastatic? Knowing your type can help you when discussing your diagnosis with your healthcare team to better understand your disease and ways to optimize treatment. Hear from women with mBC talk about their type and living with the disease and download fact sheets to better understand yours.

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