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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 one of four 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:

  • is HR-positive, including estrogen receptor (ER)-positive, progesterone receptor (PR)-positive, or both
  • is either HER2-positive or HER2-negative
  • has high levels of Ki-67

The other main breast cancer subtypes are:

  • Luminal A. Similar to luminal B, this subtype is ER-positive, PR-positive, or both — but luminal A cancer is HER2-negative and has low levels of Ki-67.
  • HER2-enriched. This subtype of breast cancer is ER-negative, PR-negative, and HER2-positive.
  • Triple-negative/basal-like. This breast cancer subtype is ER-negative, PR-negative, and HER2-negative.

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
  • overweight or obesity
  • physical inactivity
  • taking hormonal contraceptives
  • taking hormone replacement therapy after menopause
  • not having children or not breastfeeding

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 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 outside the breast.

Imaging tests like mammograms can tell you if breast cancer is likely. 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.
  • 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.

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. Includes lumpectomy or mastectomy to remove cancer cells.
  • Radiation therapy. Aims to kill cancer cells in a specific area.
  • Chemotherapy. 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:

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.

A look at the research

A small 2020 study found that triple-negative breast cancer had the poorest outlook over 5 years, but luminal B HER2-positive cancer had the poorest outlook over 10 years.

The study measured outcomes in terms of breast cancer-specific survival rate, which is the percentage of patients who did not die of breast cancer specifically over a period of time. In the study, luminal B HER2-positive cancer had a breast cancer-specific survival rate of 80.6 percent.

The same research suggested that having delivered five or more babies before diagnosis predicted poor breast cancer-specific survival. But that was only true for luminal B HER2-negative cancers. More studies are needed to explore this link.

A study published in 2016 found that, when compared to non-luminal breast cancers, luminal B breast cancer has a higher rate of local recurrence and bone metastasis. It’s worth noting that this was a retrospective analysis with a small sample size. Study authors wrote that those patients with recurrence or metastasis had a better outlook after reasonable treatment.

A larger study published in 2019 found that both age and cancer subtype are factors that can predict survival outcomes. But the researchers couldn’t say which matters the most. This study involved over 21,000 women between the ages of 20 and 89 identified in the Cancer Registry of Norway.

The researchers found that young age was associated with increased mortality due to luminal A subtype. Older age was associated with increased mortality in all subtypes. Even when adjusting for subtype, older age was linked to higher mortality.

According to the National Cancer Institute, the overall 5-year relative survival rate for breast cancer is 90.3 percent. Here’s how it breaks down by stage:

  • Localized: 99.0 percent
  • Regional: 85.8 percent
  • Distant: 29.0 percent
  • Unknown: 57.8 percent

These statistics are based on women diagnosed with breast cancer between 2011 and 2017. They don’t reflect the most up-to-date treatments or clinical trials.

Your oncologist will be able to provide a more personalized outlook for you.