Luminal B breast cancer

Luminal B breast cancer is a subtype of breast cancer named for the genes the cancer cells express. It’s also called group 2 or HR+/HER2+ breast cancer.

About 10 percent of breast cancer cases are luminal B, according to the National Cancer Institute (NCI) Surveillance, Epidemiology, and End Results (SEER) database.

The four main genetic subtypes of breast cancer

The four molecular subtypes of breast cancer may overlap, and other subtypes may look like them. The types are:

• Luminal A (HR+/HER2-)
• Luminal B (HR+/HER2+ or high Ki-67)
• Basal-like or triple negative (HR-/HER2-)
• HER2-enriched (HR-/HER2+)

The subtypes are based on the cancer tissue’s molecular characteristics—specifically, how much of proteins called hormone receptors and a protein called HER2/neu the cells express. These molecular characteristics tell doctors how the patient’s cancer may respond to various treatments and how aggressive it may be.

What is luminal B breast cancer?

Luminal B breast cancer:

• Expresses the estrogen receptor (ER+), progesterone receptor (PR+) or both
• Is HER2-positive or highly positive for the protein Ki-67, which indicates that the tumor is actively growing
• Is typically graded higher than luminal A
• Typically has somewhat poorer outcomes than luminal A
• Is likely to respond to HER2 targeted treatments 

Symptoms of luminal B breast cancer

Symptoms of luminal B breast cancer are similar to other subtypes of breast cancer. Breast cancer is often detected through screening programs before symptoms develop.

Symptoms of luminal B breast cancer may include:

• A lump or mass in the breast
• Swelling in part of or the whole breast
• Dimples in the breast skin
• Pain in the breast or nipple
• Inward-turning nipple
• Skin on the breast or nipple that is thickened, red, dry or flaking
• Unusual discharge from the nipple
• Swelling under the arm or near the collarbone

Luminal B breast cancer diagnosis and treatment

Luminal B is diagnosed the same way as other breast cancers. When a patient has symptoms of breast cancer or suspicious results from a mammogram, the doctor perform a physical exam and other imaging tests. A biopsy may be performed to remove a piece of tissue and have it tested in the lab to look for signs of cancer.

If tissue is diagnosed as cancerous, the cancer subtype may be determined using various tests.

The traditional method for determining breast cancer subtype uses a special laboratory test called immunohistochemistry, which uses dyes and enzymes to highlight certain molecules in the cells, specifically the estrogen receptor, progesterone receptor and the HER2 molecule.

New tests analyze the genetics of cancer cells obtained in a biopsy. This type of test, called advanced genomic testing, is a type of personalized medicine. These tests determine:

• The breast cancer’s subtype: ER, PR and HER2 expression
• The type of treatments that may work
• The recommended order for treatments
• The likelihood that breast cancer will return after initial treatment

MammaPrint^® is a gene expression test that may be used on any type of invasive breast cancer smaller than 5 centimeters wide that has spread to three or fewer lymph nodes. This test analyzes 70 genes to determine the risk of the cancer’s recurrence.

The Breast Cancer Index™ test predicts recurrence and responsiveness to hormone therapy in hormone receptor-positive cancers that have spread to three or fewer lymph nodes. It examines 11 genes.

Two other common gene expression tests for breast cancer, Oncotype Dx^® and Prosigna^®, are only used on HER2-negative breast cancers.

Luminal A and B breast cancer

Luminal A is the most common subtype of breast cancer—as 68 percent of breast cancers are luminal A, while only 10 percent are luminal B, according to the National Cancer Institute.

Luminal A and luminal B breast cancers are both hormone receptor-positive (HR+), with either estrogen (ER+) or progesterone receptors (PR+).

One significant difference between luminal A cancers and luminal B cancers is the presence of HER2/neu proteins. Luminal A breast cancer is typically HER2-negative. Luminal B cancers are either HER2-positive or have high levels of Ki-67, another protein that indicates high growth rates within the tumor.

Luminal A cancers have a more favorable outcome, as they’re slower growing and less aggressive. Luminal B breast cancers are faster growing, more aggressive and more challenging to treat. Luminal B has shown to be more likely to develop distant recurrence within 10 years compared to luminal A breast cancers.

Survival rates, according to the SEER:

• Five-year:
  • Luminal A: 94.4%, 5-year
  • Luminal B: 90.7%, 5-year
• Localized (only in the breast tissue):
  • Luminal A: 100%, local
  • Luminal B: 98.8%, local
• Regional (spread to nearby lymph nodes):
  • Luminal A: 90.1%, regional
  • Luminal B: 89.3%, regional
• Distant (spread further from the breast):
  • Luminal A: 31.9%, distant
  • Luminal B: 46.0%, distant

Luminal B breast cancer survival rates

According to the NCI, the overall five-year relative survival rate for HR+/HER2+ breast cancers is 90.7 percent.

When broken down by how advanced the disease is when diagnosed, the survival rates are:

• 98.8 percent for cancer that is still only in the breast tissue (localized)
• 89.3 percent for cancer that has spread to other tissues in the chest, including lymph nodes (regional)
• 46 percent for distant disease that has spread to organs in other parts of the body (distant)

Of the four molecular subtypes, luminal B has the second-most favorable survival rate following luminal A (94.4 percent). The HR-/HER+ has an 84.8 percent five-year survival rate, while the HR-/HER2- (triple-negative) breast cancers have a 77.1 percent rate.