Luminal B breast cancer is positive for estrogen and sometimes progesterone receptors. It may be positive or negative for epidermal growth factor receptor 2 and has high levels of the protein Ki-67. It grows faster compared to Luminal A.

Luminal B is a specific type of breast cancer. Each type is different, so identifying which you have is key to choosing the treatments that are most likely to help.

Read on to learn what it means to have luminal B breast cancer, how it’s diagnosed, and what you can expect from treatment.

Luminal B breast cancer is 1 of 4 main molecular subtypes of breast cancer. These subtypes are based on a molecular analysis of your cancer, including its:

  • hormone receptor (HR) status
  • human epidermal growth factor receptor 2 (HER2/neu or HER2) status
  • levels of a protein called Ki-67

Luminal B breast cancer is breast cancer that:

These characteristics of Luminal B breast cancer mean that it tends to be a bit more aggressive than Luminal A breast cancer. It may grow and spread faster. All four main breast cancer subtypes are:

  • Luminal A: This cancer is ER-positive and/or PR-positive, as well as HER2-negative.
  • Luminal B: This cancer is ER-positive and/or PR-positive, as well as HER2-positive.
  • HER2-positive: This cancer is ER-negative, PR-negative, and HER2-positive.
  • Triple-negative: This cancer is ER-negative, PR-negative, and HER2-negative.

Learn more:

There doesn’t appear to be a difference in risk factors for the molecular subtypes of breast cancer. According to a 2019 study, the major differences between the subtypes were in clinical characteristics rather than risk factors.

Factors that may increase your risk of breast cancer include:

  • being female
  • inheriting certain genetic mutations
  • family history of breast cancer
  • having your first period before age 12 or menopause after age 55
  • alcohol consumption
  • having overweight or obesity
  • physical inactivity
  • taking hormonal contraceptives
  • taking hormone replacement therapy after menopause
  • not having children or not nursing

Luminal B breast cancer has the same signs and symptoms as other breast cancers. These can include:

  • lump in the breast or underarm
  • thickening, swelling, or change in size or shape of the breast
  • red, flaky, or dimpling skin
  • nipple inversion or nipple discharge

Breast cancer doesn’t always cause symptoms in its early stages. It helps to get familiar with the way your breasts look and feel so you’ll notice changes sooner rather than later. Routine breast cancer screenings can also help detect cancer.

If you have symptoms or concerns about your breasts, talk with a doctor as soon as possible. Breast cancer is easier to treat before it spreads to other areas of the body.

Imaging tests like mammograms can tell you if there’s tissue in your breast that may be indicative of breast cancer. A biopsy of the breast tissue is the only way to confirm this. In a laboratory, the tissue will be tested for certain receptors that can fuel the growth of breast cancer. These tests can tell you about your:

  • HR status: Cancer cells that have estrogen or progesterone receptors are HR-positive.
  • HER2 status: HER2 testing with a result of 0 or 1+ means it’s HER2-negative. A result of 3+ means it’s HER2-positive. A 2+ result is called “equivocal,” and the HER2 status is unclear. HER2-low is also possible, which means there’s a presence of HER2 proteins, but not enough to be classified as HER2-positive.
  • Ki-67 levels: These proteins help measure the speed of growth and division in cancer cells. A high value means the cancer is more aggressive.

You’re not alone

Living with breast cancer can be challenging. Many people find it helpful to share their experiences with others who are going through the same thing. If you’re looking for connections, here are a few good places to start your search:

A lot goes into breast cancer treatment decisions. Aside from your cancer’s general molecular subtype, other factors your doctor will consider are:

  • age and overall health
  • tumor grade and stage at diagnosis
  • HER2 status
  • whether you’ve inherited certain genetic mutations
  • whether you’ve reached menopause
  • earlier cancer treatments, if any

Your doctor will tailor treatment to you, which may include:

  • Surgery: This includes a lumpectomy or mastectomy to remove cancer cells.
  • Radiation therapy: This uses high-energy rays or particles to destroy cancer cells in specific areas.
  • Chemotherapy: This is used to shrink tumors before surgery or to destroy cancer cells throughout the body.

Treatment also involves drugs to block the hormones that are helping cancer grow. Some of these are:

Drugs that target HER2 include:

Promising research

In 2020, scientists published a randomized phase 2 trial of neoadjuvant therapy in luminal B breast cancer. Neoadjuvant therapy is the therapy you receive before your main treatment or surgery.

Their research suggested that neoadjuvant therapy with a combination of ribociclib and letrozole could be an alternative to multi-drug neoadjuvant chemotherapy.

The trial involved high risk postmenopausal women. The women had early stage breast cancer that was HR-positive and HER2-negative. When compared to chemotherapy, the ribociclib and letrozole were found to be just as effective and better tolerated.

It’s important to note that this study was funded by Novartis Pharmaceuticals. More independent research into different approaches to treatment is ongoing.

Aside from the subtype, your individual outlook depends on many factors, such as:

  • age and overall health
  • tumor grade and stage at diagnosis
  • HER2 status
  • inherited genetic mutations
  • menopausal status
  • whether you’ve had treatment for cancer before
  • how well you respond to treatments

Luminal B breast cancer is a bit more aggressive than luminal A breast cancer. It may grow and spread faster.

According to the National Cancer Institute, the overall 5-year relative survival rate for breast cancer is 91.2%.

Here’s how it breaks down by stage:

  • Localized: 99.6%
  • Regional: 86.7%
  • Distant: 31.9%
  • Unknown: 69.7%

Is Luminal B breast cancer curable?

If the tumor is still localized, it may be possible to cure the cancer. That said, a 2020 study found that luminal B HER2-positive cancer had the poorest outlook after 10 years.

Another larger 2019 study also showed age and cancer subtype as predictors of survival outcomes, with younger age being associated with increased mortality in the luminal A subtype and older age linked to higher mortality regardless of subtype.

That said, these statistics may not reflect the most current treatments or clinical trials.

Is luminal B cancer rare?

Luminal B cancer represents about 15% to 20% of breast cancer cases.

There are different types of breast cancer, and it’s important to identify which type you have.

If you have Luminal B breast cancer, your cancer is usually positive for either estrogen or progesterone hormone receptors and is known for having high levels of the protein Ki-67. This means your tumor may grow faster, and your outlook may be less favorable.

That said, treatment is available. The earlier you’re diagnosed, the better your outlook because the tumor is less likely to have spread.