What Is Luminal B Breast Cancer?

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Luminal B breast cancer is a subtype of breast cancer. It starts in the luminal cells, which line the inside of the breast's mammary ducts.

This subtype is defined by the traits of genes that exist in breast cancer cells. It accounts for 15% to 20% of breast cancers.

Breast cancer genetic subtypes are linked by shared factors. These include the status of their hormone receptors and the human epidermal growth factor receptor 2 (HER2). The level of Ki-67 protein, which rules how fast cancer cells grow, is also assessed.

Based on these factors, luminal B breast cancer includes a wide group of tumors. This subgroup describes breast cancer that is estrogen receptor-positive and either HER2-negative or HER2-positive. The cells can have high or low levels of Ki-67 protein. Progesterone receptors may or may not be present.

When defined, these key facts can help determine the best way to treat your disease. They can also help your healthcare team predict how your cells will act and your disease outcomes.

This article explains luminal B breast cancer symptoms, causes, diagnosis, and treatment.

person with breast cancer

Daniel Llao Calvet / Getty Image

Types of Luminal B Breast Cancer

Luminal B breast cancer is one of four molecular subtypes of breast cancer. The other subtypes are identified by the following molecular characteristics:

  • Luminal A: Estrogen-receptor positive and/or progesterone receptor-positive, HER2-negative, and low Ki-67 level
  • HER2-positive: Estrogen-receptor negative, progesterone receptor negative, and HER2-positive
  • Basal-like: Estrogen receptor-negative, progesterone receptor-negative, and HER2 negative (also called triple-negative breast cancer)

Luminal B breast cancer includes a heterogeneous group of tumors with different molecular characteristics. Generally, luminal B breast cancer can be classified into one of the following categories based on common genetic factors:

  • Luminal A-like breast cancer: Estrogen receptor-positive; HER2-negative, low Ki-67, and high progesterone receptor levels
  • Luminal B-like breast cancer: Estrogen receptor-positive, HER2-negative, with high Ki-67 or low progesterone receptor levels
  • Luminal B breast cancer: Estrogen receptor-positive and HER2-positive, and any level of Ki-67 or progesterone receptor levels

Luminal B Breast Cancer Symptoms

Like other types of breast cancer, symptoms of luminal B breast cancer can vary widely. It can even occur without any symptoms in its early stages. Generally, symptoms of luminal B breast cancer are not unique from those that occur with other types of breast cancer.

You may recognize symptoms of breast cancer during a breast self-exam; they can also be identified during a medical breast exam or mammogram.

Common symptoms that occur with all types of breast cancer include the following:

  • A lump in your breast
  • Skin dimpling on the breast that makes it resemble an orange peel
  • An inverted nipple
  • Redness, flaking, dryness, or thickening on the nipple or breast
  • Nipple discharge other than breast milk
  • Scaly, red, or swollen skin in the nipple area or the breast
  • Pain in the breast or nipple
  • Swelling in or around the breast, lymph nodes under the arm, or near the collar bone
  • Any change in the normal shape or size of the breast

Contact your healthcare provider promptly if you notice any of these changes in your breasts. While these symptoms don't always indicate the presence of breast cancer, they can be related to other noncancerous (benign) breast conditions. Treating breast cancer or any health problem is easiest when it's done at the earliest stages.


The exact causes of luminal B breast cancer, and all types of breast cancer, are not known. Research indicates there are no substantial risk factors for developing luminal B cancer over any other molecular subtype.

Certain aspects of your genetics can increase your risk of developing any type of breast cancer. You have the highest risk for breast cancer if you have a strong family history of breast or ovarian cancer. Hereditary gene defects account for up to 10% of breast cancers.

Defects in BRCA1 (breast cancer gene one) or BRCA2 (breast cancer gene two) are responsible for most types of inherited breast cancer. Having one of these gene mutations gives you a 70% chance of getting breast cancer by age 80.

The following factors can also increase your risk of developing any type of breast cancer:


Determining whether you have the luminal B breast cancer subtype or another subtype of breast cancer is done after your healthcare provider confirms you have breast cancer.

When any type of breast cancer is suspected, your healthcare provider will use one or more of the following imaging tests to examine the inside of your breasts and identify the presence of abnormal areas of breast tissue:

If the results of an imaging test suggest the presence of breast cancer, a breast biopsy may be used to confirm the diagnosis. This procedure involves the surgical removal of a sample of breast tissue for examination under a microscope.

When breast cancer is confirmed, your healthcare provider will likely use one or more of the following additional tests to identify the markers that are used to categorize breast cancer as luminal B or another subtype:


Identifying your molecular subgroup of breast cancer can provide valuable information to help your healthcare team find the most effective treatment for your disease. These findings are combined with information about your medical and family histories, tumor grade (how normal or abnormal cancer cells and tissue look) and stage (size of tumor and whether the cancer has spread from the initial site) at diagnosis, HER2 status, menopause status, age, and overall health to make these choices.

Treatment for luminal B breast cancer often starts with breast surgery to remove the cancer cells. This can involve one of the following surgical procedures:  

You may also benefit from one of the following treatments to destroy breast cancer cells after surgery:


Many factors contribute to a cancer prognosis. Generally, luminal B breast cancers have higher levels of genes that cause cancer to proliferate or reproduce. Cancer cells in luminal B breast cancer respond to the hormone estrogen and are generally HER2 positive. This promotes fast growth and the greater likelihood of the disease spreading compared to other breast cancer subtypes.

Compared to the luminal A subtype of breast cancer, tumors in luminal B breast cancer are linked with a poorer prognosis and lower survival rates after relapse. Luminal B breast cancer is more likely to have the following characteristics that affect prognosis:

  • Tumors that are larger and more aggressive
  • Poorer tumor grade
  • Involvement of the lymph nodes (lymph node positive)
  • Increased relapse rates within the first five years after diagnosis
  • Higher recurrence rate

According to the National Cancer Institute, the breast cancer subtype can affect survival, but the stage of cancer at diagnosis may be the most important consideration when determining survival outcomes. Patients with localized breast cancer, which is confined to the place it started, have the highest survival rates.


A diagnosis of luminal B breast cancer can be challenging. Treatment can involve multiple approaches, including surgery, chemotherapy, and long-term hormone therapy.

The physical and emotional effects of the disease and treatment can be difficult to endure. Don't hesitate to accept help from willing family members and friends so you can preserve your strength for healing and recuperation.

The emotional aspects of the disease can be just as overwhelming as the physical effects. To cope, you may find it helpful to share your experiences with other people who are experiencing the same types of challenges.

Consider joining a breast cancer support group to connect with other breast cancer patients. If you can't find a local group, seek out an online support group.


Luminal B breast cancer is one of four genetic subtypes of breast cancer. It is defined by key factors of genes in the breast cancer cells.

This subtype affects the luminal cells inside the mammary ducts. It includes up to 20% of breast cancers.

Often, the tumors in this subgroup tend to be more aggressive, larger, and recur more often than the luminal A subtype. As a result, luminal B breast cancer can point to poorer outcomes.

A Word From Verywell

Many factors affect the way your disease acts and the outcomes you experience. Generally, the prognosis for all types of breast cancer has improved in recent years. Early disease detection and treatments personalized to specific breast cancer types have helped achieve this progress.

Knowing your breast cancer subtype is more important in the consideration of your treatment than it is in making your prognosis. Ongoing breast cancer research continues to improve treatment outcomes and reduce the incidence of cancer recurrence.

If current breast cancer therapies don't provide the treatment you need, talk to your healthcare team about the option of joining a clinical trial. Doing so may provide you with safe access to new drugs, treatments, or procedures as soon as possible.

Frequently Asked Questions

  • Why is hormone therapy often used to treat luminal B breast cancer?

    Hormone therapy blocks the body's ability to produce hormones or prevents hormones from affecting breast cancer cells. This can slow or stop the growth of hormone-sensitive tumors. Since all luminal B breast cancer is estrogen receptor-positive, hormonal therapy that targets the estrogen receptors can be effective.

  • What is the best treatment for luminal B breast cancer?

    Treatment for any type of breast cancer depends on many factors. In addition to your cancer subtype, your healthcare team considers other details like your age, personal and family medical histories, stage of the disease at diagnosis, and whether you're in menopause when choosing your treatment. While chemotherapy, hormone therapy, and targeted HER2 treatment can be effective against luminal B breast cancer, your advised treatment may be different based on your personal situation.

  • Am I at risk for luminal B breast cancer?

    It's impossible to determine who is at risk for luminal B breast cancer or any other subtype of the disease. While luminal A breast cancer is the most common subtype, it's not known why one subtype occurs over another. In a study of risk factors and their impact on different subtypes, researchers reported that known risk factors were similar among the four major breast cancer genetic subtypes, making it hard to predict the risk of developing one subtype over another.

10 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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By Anna Giorgi
Anna Zernone Giorgi is a writer who specializes in health and lifestyle topics. Her experience includes over 25 years of writing on health and wellness-related subjects for consumers and medical professionals, in addition to holding positions in healthcare communications.