Luminal A Breast Cancer

April 10, 2025

This page was reviewed under our medical and editorial policy by Nikhila Kethireddy, M.D., assistant clinical professor, and Susan Yost, Ph.D., staff scientist, Department of Medical Oncology & Therapeutics Research, City of Hope^® Cancer Center Duarte

Breast cancer has different molecular subtypes, or smaller categories of the disease based on its features. Luminal A is one of these subtypes. It is a common subtype among those diagnosed with breast cancer and accounts for about 68% of cases.

Breast cancer molecular subtypes also include:

• Luminal B breast cancer, which accounts for about 10% of breast cancers
• Basal or triple-negative breast cancer (TNBC), which accounts for about 10% of breast cancers
• Human epidermal growth factor receptor 2 (HER2)-enriched (HER2E), which accounts for about 10% to 15% of breast cancers, and in some cases may also be a subset of luminal B breast cancer

What Is Luminal A Breast Cancer?

Three main molecular features must be present in breast cancer cells for the disease to be considered luminal A breast cancer.

Hormone receptor-positive: Cells have different types of proteins that bind to certain hormones. These proteins are called hormone receptors. Luminal A has cancer cells containing estrogen receptors (estrogen-binding proteins) and progesterone receptors (progesterone-binding proteins). This makes luminal A an estrogen receptor-positive (ER+) and progesterone receptor-positive (PR+) cancer. More generally, breast cancer that is ER+ or PR+ (or both) is sometimes called hormone receptor-positive (HR+). Breast cancers like luminal A that are HR+ use the estrogen and progesterone hormones to grow and spread.

HER2-negative: HER2 is a protein in cells that helps speed up cell growth. Luminal A cancer cells have little to no HER2 protein on their surfaces; therefore, the disease is considered HER2-negative (HER2-). This is one reason luminal A cancer tends to grow slowly.

Low Ki-67: Ki-67 is a protein that helps cells grow and divide and is a cellular marker of proliferation. Luminal A breast cancer is marked by low levels of Ki-67 in its cancer cells, another reason they tend to divide and spread slowly.

A doctor called a pathologist tests levels of these proteins in cancer cells using a tissue sample taken during a breast biopsy to determine if the patient has luminal A breast cancer. He or she may also test for certain gene changes (mutations), such as mutations on the PIK3CA gene, because it has been known to occur in luminal A breast cancers.

Because of its hormone receptor-positive status and HER2 protein-negative status, luminal A is also sometimes referred to as HR+/HER2- breast cancer.

Luminal A Versus Luminal B Breast Cancer

Luminal B is a subtype of breast cancer that has both similarities and differences with luminal A breast cancer. For instance:

• Both have estrogen receptors, making them estrogen receptor-positive (ER+) and hormone receptor-positive (HR+)
• Luminal B does not typically have progesterone receptors, making it PR-, while luminal A usually does, making it PR+
• Luminal B may or may not have high levels of the HER2 protein that helps cancer cells grow fast, meaning it is either HER2+ or HER2-, while luminal A has low or no levels of this protein, making it HER2- Luminal B usually has high levels of Ki-67 protein that helps cancer cells divide and grow, and luminal A has low levels of this protein
• Luminal B tends to grow faster than luminal A, and the prognosis (chance of recovery) is typically worse
• Luminal B accounts for about 10% of breast cancer cases — almost 7 times less than luminal A breast cancer cases.

According to researchers, both luminal A and luminal B saw an increase in cases between 2010 and 2016 among certain populations. For example:

• Luminal A cases increased for non-Hispanic white women between 40 to 69 years of age, non-Hispanic Black women between 55 and 69 and Asian/Pacific Islander women between 40 and 69 years of age
• Luminal B cases increased for non-Hispanic white women and Hispanic women of all ages

Is Luminal A Breast Cancer Hereditary?

Luminal A may or may not be hereditary. Research is ongoing into inherited (passed down from a parent to a child) and somatic (acquired changes over time) gene mutations that may lead to this subtype of the disease.

The risk factors for luminal A breast cancer are strongly associated with the overall risk factors for breast cancer. One of those breast cancer risk factors is inherited gene changes that may help breast cancer cells grow and spread. Today, about 5% to 10% of breast cancer cases overall are inherited. A family history of breast cancer is also a risk factor for luminal A breast cancer, which may suggest a hereditary gene in some cases.

A mutation (change) in the BRCA gene is the most common inherited breast cancer gene. Patients diagnosed with luminal A and a BRCA mutation will be treated with certain drugs and treatment protocols that may differ from the treatment plan for those without this mutation.

Knowing if a patient’s luminal A breast cancer shows certain genetic changes helps doctors plan and optimize treatment protocols for each person, and that is why gene expression testing is done during the diagnostic process.

Luminal A Breast Cancer Symptoms

For the majority of breast cancers, the main symptom is a painless, hard lump in the breast or a soft lump or mass that is tender or painful. However, breast cancer symptoms may not be present at all, and a screening mammogram is often used to help diagnose the disease.

If people do experience symptoms of luminal A breast cancer, they may include:

• Partial breast thickening or swelling
• Breast pain
• Breast size and shape changes
• Dimpling or irritation of the breast skin
• Nipple pain or pulling sensations; discharge (that is not breast milk); retraction (turned inward); or dry, flaking or thickened skin
• Breast skin that is red, dry, thickened or flaking
• Lymph node swelling in the collarbone or armpit region

Breast cancer that is diagnosed and treated in its early stages typically has a better prognosis than more advanced cancer. That is why patients experiencing these or other breast symptoms should contact their doctor immediately so that tests may be performed to determine if breast cancer is present or if the changes are caused by other health conditions.

Luminal A Breast Cancer Treatment

Because luminal A breast cancer cells are hormone receptor-positive, hormone therapy drugs that block estrogen and progesterone from attaching to these cancer receptors or that lower hormone levels are given to patients for early-stage and locally advanced stage cancer. In addition, breast-conserving surgery (lumpectomy) or removal of the entire breast (mastectomy) may be performed.

Depending on the breast cancer’s stage, hormone therapy may be given before, after, or both before and after the surgical procedure. It is usually continued for a minimum of five years.

Certain targeted therapy drugs for breast cancer like Verzenio^® (abemaciclib), Kisqali^® (ribociclib) and Ibrance^® (palbociclib), which block proteins that help hormone receptor-positive cancer cells divide, may also be used as treatment for luminal A.

Breast cancer that is HR+ and HER2- like luminal A tends to be less sensitive to chemotherapy anticancer drugs than other types of breast cancer. For this reason, doctors do not always turn to breast cancer chemotherapy as the first choice to help shrink luminal A breast tumors, but instead may perform additional tests to help determine how well the cancer may respond to this treatment.

The other noteworthy treatment protocol with luminal A breast cancer is that there may be some exceptions to the recommendation of using radiation therapy after breast-conserving surgery (BCS) to treat the disease. According to a 2023 study, patients aged 55 and older with Stage 1 low-grade (likely slow-growing and spreading) luminal A breast cancer and a low percentage of tumor cells with the Ki-67 protein may be able to avoid radiation therapy for breast cancer after BCS without an increased risk of cancer recurrence (return).

For patients who have luminal A that has spread to distant parts of the body (metastatic luminal A), hormone therapy and targeted drug therapy may also be given alongside treatments such as chemotherapy and radiation therapy for breast cancer to help alleviate symptoms that may be causing discomfort.

Luminal A Breast Cancer Prognosis

Luminal A breast cancer is responsive to treatments. The five-year relative survival rate was 100% for women diagnosed with HR+/HER2- breast cancer in the cancer’s early stage (when there is no indication it has spread outside the breast) between 2014 and 2020, according to the National Cancer Institute (NCI) SEER (Surveillance, Epidemiology, and End Results Program) database.

The stage (extent of cancer in the body) at the time a woman is diagnosed with luminal A does significantly impact this survival rate. The five-year relative survival rate for the condition was:

• 90.5% when diagnosed after spreading to area lymph nodes (regional cancer)
• 35.4% when diagnosed after spreading to distant parts of the body (distant cancer)
• 95.1% overall

For women under age 50 and non-Hispanic Black women diagnosed with luminal A, or HR+/HER2- cancer, the overall five-year relative survival rate was slightly lower — 93.5% and 89.5%, respectively.

However, at every stage and overall — including for women under age 50 and non-Hispanic Black women — luminal A’s prognosis is better than the five-year relative survival rate for female breast cancer as a whole.

Breast Cancer Care at City of Hope

City of Hope is leading evidence-based research to learn how breast cancer treatments like hormone therapy may affect different groups of women in order to create individualized care plans that improve each patient’s prognosis. This is combined with advanced diagnostic tests, such as receptor testing to check for progesterone and estrogen proteins, and genetic testing to discover if the patient’s breast cancer is hereditary. Once diagnosed, the patient and their loved ones are guided through thoughtful, innovative treatment options aimed at reducing recovery times and increasing successful outcomes.