Glossary | Breast Cancer Research Foundation

AC regimen

“AC” is an abbreviation for the chemotherapy drugs Adriamycin® (doxorubicin hydrochloride) and cyclophosphamide. The two are given in combination either before surgery (neoadjuvent therapy) or after surgery (adjuvant therapy) to kill breast cancer cells. Both are administered intravenously and may be used with other treatments.

Adjuvant therapy

Adjuvant therapies are treatments given after the initial treatment of breast cancer (surgery) to reduce the chance of the cancer returning. Some examples of adjuvant therapy include chemotherapy, radiation therapy, and endocrine therapy. Your doctor may recommend you undergo one or more of these treatments.

Advanced breast cancer

See metastatic breast cancer.

American Association for Cancer Research

The American Association for Cancer Research (AACR) promotes research and education related to the causes, diagnosis, treatment, and prevention of cancer. It is the first and largest professional organization dedicated to advancing cancer research. BCRF partners with AACR to give grants to scientists who conduct promising breast cancer research.

American Society for Radiation Oncology

The American Society for Radiation Oncology (ASTRO) is focused on improving cancer care by educating and training medical professionals who treat patients with radiation therapy, among other goals. BCRF works with ASTRO to advance breast cancer science and research.

American Society of Clinical Oncology

Like AACR, the American Society of Clinical Oncology (ASCO) partners with BCRF to advance breast cancer research. The organization also promotes lifelong learning for oncologists, access to quality cancer care, and more. ASCO is supported by the Conquer Cancer Foundation, which funds research and programs that improve the lives of people with cancer.

American Society of Preventive Oncology

The American Society of Preventive Oncology (ASPO) is dedicated to preventing the development and progression of cancer. BCRF works with the organization to support groundbreaking breast cancer research.

Anastrozole

This medication is part of a class of drugs called aromatase inhibitors, which are used to treat breast cancer in postmenopausal women. Anastrozole is a hormone therapy drug that works by lowering levels of estrogen—a hormone that can promote growth of breast cancer cells. It is administered orally.

Androgen

Sometimes referred to as “male hormones,” androgens are a type of hormone that plays a role in the growth and development of the male reproductive system. However, women also produce androgens, and these hormones can drive breast cancer growth. Emerging research suggests drugs that interfere with androgens and their actions—referred to as androgen receptor (AR)–targeted therapies, AR blockers, AR antagonists, or anti-androgen therapy—could be used to treat types of breast cancer that express the androgen receptor, such as triple-negative breast cancer.

Angiogenesis

This is the process by which blood vessels form from existing vessels. Angiogensis is a natural event that occurs throughout life and is an essential part of growth and healing. However, angiogenesis can be harmful in diseases such as cancer. Cancer cells are able to hijack the formation of new blood vessels to supply themselves with nutrients and oxygen, thereby allowing them to continue to grow and spread (metastasize).

Angiogenesis inhibitors

These drugs block the formation of new blood vessels that provide nutrients and oxygen to tumor cells (angiogenesis). Their action “starves” the tumor, which can slow its growth or cause it to shrink. Angiogenesis inhibitors do not destroy the tumor itself, so they are used in conjunction with other anti-cancer treatments.

Anthracyclines

A type of antibiotic drug, anthracyclines are commonly used in chemotherapy to kill cancer cells by damaging the cells’ DNA. They may be given before surgery (neoadjuvent therapy) or after surgery (adjuvant therapy). Adriamycin (see AC regimen) is an angiogenesis inhibitor.

Anti-androgen therapy

This type of treatment is used to prevent growth of androgen-sensitive tumors. While it’s commonly used to treat prostate cancer, emerging research suggests that anti-androgen therapy may have a role in treating types of breast cancer that express the androgen receptor, such as triple-negative breast cancer.

Aromatase inhibitor

A type of hormone therapy drug, aromatase inhibitors are used to treat breast cancer in postmenopausal women. They work by preventing the enzyme aromatase from converting androgens into estrogen, thereby decreasing estrogen production in the body. Aromatase inhibitors are used to treat breast cancers that depend on estrogen to grow; these types of breast cancer are referred to as hormone– or estrogen receptor–positive breast cancer.

Basal-like breast cancer

This aggressive subtype of breast cancer is similar to triple-negative breast cancer (TNBC) in that it is usually hormone receptor–negative, meaning it lacks receptors for estrogen, progesterone, and HER2. The terms basal-like breast cancer (BLBC) and TNBC are sometimes used interchangeably. However, even though these two types overlap significantly, not all TNBC tumors are considered basal-like (based on the genes they express), and not all basal-like tumors are triple-negative. “Basal-like” refers to the fact that BLBC cells resemble the basal cells found in the glandular tissue of breast.

Biomarker

Short for “biological marker,” a biomarker is a biological molecule that physicians use to learn more about a patient’s disease. Examples of cancer biomarkers include proteins and gene mutations. Biomarkers can be used to detect the presence of breast cancer, determine its subtype, and identify people who are at increased risk of developing the disease. In addition, these molecules can be used to predict a patient’s response to particular anti-cancer therapies, so physicians can use them to guide treatment decisions. Biomarkers are typically measured by taking a blood or tissue sample. Identifying new biomarkers is crucial to advance breast cancer research.

Biopsy

In this test, a patient’s tissue sample is examined under a microscope by a pathologist (a doctor who specializes in the origin, nature, and course of disease) to look for signs of cancer. Biopsies may be performed via suction through a needle or vacuum-powered probe, or doctors may surgically remove a portion of the breast mass. If cancer is detected, the pathologist will write a report for your doctor that includes information that will inform your care, such as the type of breast cancer you have and how likely it is to grow and spread.

BRCA genes

Short for BReast CAncer, the BRCA genes—BRCA1 and BRCA2—produce proteins that prevent healthy cells from becoming malignant (cancerous). Everyone has BRCA genes, but people with inherited mutations in the BRCA genes are at significantly higher risk of developing breast and other cancers, including ovarian, prostate, and pancreatic. Mutations in the BRCA genes are relatively rare, but they are more common among certain groups of people, notably those of Ashkenazi Jewish descent. Genetic testing is available for BRCA1 and BCRA2 mutations, but due to their rarity, testing is only recommended for those whose personal or family history suggestions mutations are present.

Breast density

Breast density refers to the relative amount breast tissue types seen on a person’s mammogram. It is not related to the size of your breasts or how they feel. Dense breasts have a greater amount of dense tissue—milk glands, milk ducts, and supportive tissue (stroma)—compared to non-dense (fatty) tissue. The denser a person’s breasts, the harder it is for radiologists to detect breast tumors on a mammogram. Having dense breasts is considered a breast cancer risk factor, though experts aren’t certain why they increase the risk of developing the disease.

Breast reconstruction

Women who have undergone surgery to remove one or both breasts to treat or prevent breast cancer may have the option of rebuilding their breast(s)—a process called breast reconstruction. This can be accomplished using artificial implants or tissue from another part of the body (called autologous tissue reconstruction). Your physician may recommend either immediate or delayed reconstruction, depending on the type of breast cancer you have and whether you’ll be undergoing radiation therapy.

Breast-conserving surgery

In this procedure, surgeons aim to remove the patient’s breast cancer but not the entire breast. Some normal tissue surrounding the cancer will be excised as well, and lymph nodes under the armpit and part of the chest wall lining may also be removed. Breast-conserving surgery (BCS) may be an option for patients who meet certain criteria (small tumor size, cancer located in just one area of the breast, etc.). BCS is also referred to as a partial mastectomy, lumpectomy, or breast-sparing surgery.

Calcifications

These are deposits of calcium that develop in breast tissue. There are two types of calcifications that may appear on a person’s mammogram: large white deposits called macrocalcifications and fine white specks of calcium called microcalcifications. Both types are usually benign and may be caused by past injuries to or infections in the breast or benign (noncancerous) growths in the breast, such as fibroadenomas. However, clusters of microcalcifications may suggest the presence of breast cancer. If these clusters are detected, further diagnostic tests or an additional mammogram with greater magnification will be required.

Cancer-associated fibroblast

A cancer-associated fibroblast (CAF) is a type of cell found in the supportive tissue (stroma) that surrounds a breast tumor and helps it grow and thrive. CAFs may also play a role in the spread (metastasis) of breast cancer to other locations in the body. They are also referred to as tumor-associated fibroblasts, carcinogenic-associated fibroblasts, or activated fibroblasts.

CDK4/6 inhibitor

Cyclin-dependent kinases (CDKs) are proteins found in healthy and cancerous cells that control how quickly cells grow and divide. They were discovered by BCRF investigator Sir Paul M. Nurse, PhD, FRS. CDKs can become overactive and cause cells, including breast cancer cells, to grow and divide uncontrollably. CDK4/6 inhibitors interrupt specific CDKs to slow or even stop cancer cells from growing. CDK4/6 inhibitors were game-changing treatments for metastatic breast cancer because they significantly extended patients’ survival. Now they're being used for treating high-risk, early-stage hormone-positive breast cancers to reduce recurrence.

Cell-free DNA

These are small, degraded fragments of DNA that circulate in the blood plasma and other bodily fluids. Cell-free DNA (cfDNA) is found in higher amounts in people who have cancer, and research shows it may be a useful biomarker for the disease. For example, physicians can monitor treatment response and detect resistance to treatment by measuring cfDNA in a patient’s blood plasma. cfDNA is also referred to as circulating tumor DNA (ctDNA) and circulating nucleic acid.

Chemotherapy

Chemotherapy is a form of treatment in which patients are given one or more drugs to kill rapidly dividing cells in the body. It is used to treat cancer because cancer cells grow and divide faster than other types of cells. Chemotherapy also has an impact on healthy tissues with rapid cell turnover, such hair, bone marrow, skin, and the digestive system. It may be used before surgery (neoadjuvent therapy) or after surgery (adjuvant therapy). Chemotherapy may be administered via injection or infusion, and it can also be given orally or applied to the skin. It can be used alone or in combination with other types of treatment, such as hormone therapy and radiation therapy.

Circulating tumor cells

These are cancer cells that a tumor sheds into the blood and lymphatic stream, allowing them to travel to other parts of the body. Circulating tumor cells (CTCs) are a type of biomarker and are detected via liquid biopsy. They may be used to evaluate the likelihood that a cancer will spread.

Clinical trial

A clinical trial is a type of study conducted in human participants. Researchers use clinical trials to evaluate the effectiveness and safety of new ways to prevent, detect, and treat disease. These studies are also used to investigate different combinations of treatments and test new approaches to existing therapies such as surgery and radiation. There are five phases (phase 0 to phase IV) of clinical trials, and participants can enroll during any phase as long as they fit the eligibility requirements. If you’re interested in taking part in one, talk to your physician.

Cohort study

The word “cohort” describes a group of people. In a cohort study, researchers follow two or more cohorts who share a particular characteristic—such as age, sex, etc.—to identify associations between exposures and disease. For example, a researcher may follow a cohort of women who smoke and a cohort of women who are former smokers to determine and compare breast cancer incidence rates in both groups.

CT scan

Short for “computed tomography” scan, a CT scan is conducted by taking X-rays from multiple angles. The X-ray machine is connected to a computer, which stacks the images to generate a 3D view of tissues and organs. Sometimes, a dye is injected into a patient’s vein or swallowed by mouth prior to the procedure to improve the image resolution. CT scans may be used to detect breast cancer, determine whether the disease has spread, monitor response to treatment, and more. A CT scan is also sometimes referred to as a CAT scan.

Cumulative risk

In cancer research, cumulative risk describes the likelihood that a person will develop a particular type of cancer by a certain age. This measurement can change depending on a person’s individual risk factors for the disease. The cumulative risk that a woman with no known risk factors develops breast cancer before the age of 90 is approximately 12 percent.

Cytoskeleton

The cytoskeleton of a cell provides its framework and structure and maintains its shape. It also plays an essential role in cell division. The anti-cancer drug paclitaxel (Taxol®) works by interfering with the cytoskeleton to prevent cell division, thereby killing cancer cells and stopping cancer growth.

Disease-free survival

This is the amount of time following primary treatment for breast cancer when a patient has no symptoms of the cancer. Disease-free survival (DFS) is a way to measure a patient’s response to treatment in a clinical trial. It is synonymous with relapse-free survival (RFS).

Distant recurrence

When a patient’s cancer returns in other organs far from the original site, , such as the lungs, bones, or brain, it is referred to as a distant or metastatic recurrence.

DNA

DNA, short for “deoxyribonucleic acid,” is the genetic information that is passed on from one generation to the next. It contains a person’s unique genetic code. Sometimes, mutations (changes) are present in the genetic code, which may be inherited or acquired. These mutations can be dangerous when the body can’t repair them and may lead to changes in the behavior or structure of a person’s genes. Researchers have identified many gene mutations that contribute to breast cancer, including the well-known inherited BRCA genes.

DNA sequencing

In this process, a biological sample is collected (via biopsy, for example) to determine the sequence (order) of the four building blocks that make up the genetic code of a person’s cells. DNA sequencing can be used to identify mutations that may reflect changes relevant to a cancer patient’s diagnosis, treatment, or cumulative risk.

Dose-dense therapy

This is a chemotherapy treatment plan developed to maximize the destruction of cancer cells and minimize the harm to healthy tissue (toxicity). In a dose-dense chemotherapy regimen, the patient receives each dose of the drug(s) more frequently. Because this treatment approach also kills cells that make up the body’s immune defense system, it is often paired with drugs that stimulate the immune system to allow for quicker recovery. Dose-dense therapy is also referred to as sequential-dose density.

Drug resistance

This occurs when cancer fails to respond to a treatment. Sometimes, cancer cells are resistant to a particular treatment; in other cases, the drug may work at first, but the cells acquire changes during treatment that cause them to develop resistance. Identifying ways to overcome drug resistance is a major area of breast cancer research.

Ductal carcinoma in situ (DCIS)

In ductal carcinoma in situ (DCIS)—also called stage 0 breast cancer—abnormal changes are present in the cells that line the breast’s milk ducts. It is a pre-invasive or non-invasive breast cancer, meaning it has not spread outside the milk ducts to other tissues in the breast. If DCIS goes undetected and untreated, however, it can spread to nearby tissue, at which point it is invasive breast cancer. DCIS can be treated with a lumpectomy or mastectomy, depending on the size and number of areas in the breast that are affected.

Endocrine therapy

Endocrine therapy, or hormone therapy, is a type of treatment that slows or stops the growth of hormone-sensitive breast tumors. It does so by preventing the body from producing estrogen and progesterone—hormones that promote the growth of some breast cancers—or interfering with the effects these hormones have on cancer cells. Endocrine therapies may be to treat breast cancers that rely on hormones to grow, such as estrogen receptor (ER)–positive breast cancer.

Epigenetics

This area of study is focused on the ways in which the function of our genes can be turned on or off without alterations to a person’s genetic code. Epigenetic changes play a role in several types of cancer, including breast cancer. Scientists hope that by manipulating these changes, significant improvements could be made in the detection, prevention, and treatment of cancer.

Estrogen

This hormone—often referred to as the “female hormone”—serves many important purposes, including developing and maintaining female sex characteristics. It is produced by the body, and it can also be produced in a laboratory for use as birth control or to treat menstrual disorders, osteoporosis, symptoms of menopause, and other conditions. Unfortunately, estrogen can also promote the growth and spread of certain forms of cancer, including breast cancer. Patients whose breast cancer cells have estrogen receptors and are fueled by estrogen are diagnosed with estrogen receptor (ER)–positive breast cancer.

Estrogen receptor

The estrogen receptor (ER) is a protein found in and on certain cells in the body that binds to the hormone estrogen. Healthy breast cells have ERs, as do some breast cancer cells. When estrogen binds to certain breast cancer cells, it fuels breast cancer’s growth and spread.

Estrogen receptor–negative

Breast cancer cells that don’t require estrogen to grow and spread are considered estrogen receptor (ER)–negative. These cancer cells have few or no ERs.

Estrogen receptor–positive

Breast cancer cells that have ERs and require estrogen to grow and spread are considered estrogen receptor (ER)–positive. ER-positive breast cancer is the most common type of breast cancer diagnosed today.

Etiology

An area of study focused on the causes or origins of a disease.

Exemestane

This drug—an aromatase inhibitor taken orally—lowers the amount of estrogen produced in the body. It is used to treat certain patients who have either early-stage estrogen receptor (ER)–positive breast cancer or metastatic breast cancer. Postmenopausal women whose cancer has already been treated with tamoxifen may also be treated with exemestane.

Genetic testing

In this type of test, a person’s tissue or cell sample is evaluated to see if genetic changes associated with a disease or an increased risk of developing a disease are present. For example, mutations (changes) in genes that are known to increase the risk of developing breast cancer can be detected through genetic testing. If any of these mutations are identified, this information can be used to prevent, diagnose, and treat cancer. Genetic testing has limitations, however, because the presence of a mutation does not mean the person will definitely develop the disease in question. If you’re considering genetic testing, it’s important to first discuss the pros and cons of doing so with a geneticist or genetic counselor.

Genome

This term refers to an organism’s complete set of genetic material. The genome contains all of the information necessary to build and grow an organism. One area of research, cancer genomics, aims to identify the exact genetic mutations (changes) that may cause an individual’s cancer. Findings from this type of research advance precision medicine.

Germline DNA

Germline DNA is the DNA in the germ cells, which are the egg and sperm cells that join to form an embryo. Mutations (changes) that predispose people to certain diseases can occur in these cells—called germline mutations—and can be passed to future generations. Inherited mutations in the BRCA genes are an example of germline mutations.

Grade (of breast cancer)

When a person is diagnosed with breast cancer, the tumor(s) are assigned a grade to inform treatment decisions. The grade provides information about the rate by which the cancer is likely to grow and its tendency to spread. Grades—ranging from 1 to 3—are based on how abnormal the cancer cells appear under a microscope. Grade 1 means the cancer cells look similar to normal breast cells and indicate they are slow growing, while grade 3 means the cells do not look normal and tend to grow and spread aggressively.

HER2

HER2, which is short for “human epidermal growth factor receptor 2,” is a growth-promoting receptor (protein) found on the surface of normal cells, including breast cells. HER2 receptors can also be found in excess on certain breast cancer cells, and these cells are called HER2-positive. HER2-positive breast cancer tends to grow and spread faster than other breast cancers. HER2 is also referred to as HER2/neu, c-erbB-2, and human EGF receptor 2.

HER2-negative

This term (sometimes abbreviated as HER2-) describes breast cancer cells that do not have an excessive number of HER2 receptors on their surface.

HER2-positive

HER2-positive (HER2+) cancer cells have an excessive amount of growth-promoting HER2 receptors on their surface. HER2-positive breast cancers tend to be more aggressive than those that are HER2-negative.

Herceptin

This drug (generic name: trastuzumab) is used to treat HER2-positive (HER2+) breast cancer. Herceptin may be given on its own or in combination with other anti-cancer drugs. It is part of a class of drugs called monoclonal antibodies, which are used to treat cancer, autoimmune diseases, and other conditions. Herceptin treats HER2-positive breast cancer by targeting HER2 receptors, which are proteins found on the surface of some breast cancer cells. It is typically administered intravenously.

Hormone receptor

These proteins, which may be present on the surface of or inside cells, bind to certain hormones. Breast cancer cells that have hormone receptors are described as hormone receptor–positive and rely on hormones to grow. The two types of hormone receptors that may be present in or on breast cancer cells are estrogen receptors and progesterone receptors.

Hormone receptor–positive

Breast cancers are described this way when their cells have hormone receptors (proteins that bind to certain hormones) and rely on hormones to grow. The two types of hormone receptors that may be present in or on breast cancer cells are estrogen receptors and progesterone receptors.

Hormone therapy

See endocrine therapy.

Immunotherapy

This treatment uses the power of a person’s immune system to fight diseases such as cancer. Immunotherapy works in a variety of ways, depending on the drug(s) used. Some improve the body’s ability to “see” and destroy cancer cells, for example, while others allow immune cells to respond more strongly to cancer. Immunotherapy is a major area of breast cancer research.

Inflammatory breast cancer

This is a rare and aggressive type of breast cancer in which cancer cells block the lymph vessels in the skin of the breast. Inflammatory breast cancer (IBC) is unique in its appearance. It usually doesn’t cause a lump; rather, the breast may be discolored or red, swollen, and may feel itchy and warm to the touch. The skin is typically thickened and may have a pitted appearance (similar to the skin of an orange), and the nipple may become inverted (pulled into the breast).

Invasive breast cancer

Invasive breast cancer occurs when breast cancer cells spread beyond the ducts or lobules of the breast and into the surrounding breast tissue or other parts of the body.

Invasive ductal carcinoma

This type of breast cancer begins in the lining of the milk ducts that transport milk to the nipple and invades the surrounding breast tissue. It can potentially spread to the lymph nodes and other parts of the body. Invasive ductal carcinoma (IDC) is the most common type of invasive breast cancer. It is also referred to as infiltrating ductal carcinoma.

Invasive lobular carcinoma

Invasive lobular breast cancer (ILC) begins in the lobules (milk-producing glands) of the breast and invades the surrounding breast tissue. It can potentially spread to the lymph nodes and other parts of the body. It is the second most common type of invasive breast cancer. It is also referred to as infiltrating lobular carcinoma.

Letrozole

Like anastrozole and exemestane, letrozole belongs to a class of called drugs aromatase inhibitors. It used to treat breast cancer in postmenopausal women. Letrozole is a type of hormone therapy, administered orally, that decreases the amount of estrogen produced by the body, stopping or slowing the growth of breast cancer cells that rely on that hormone.

Lifetime risk

In cancer research, lifetime risk describes the likelihood that a person will develop a certain type of cancer during his or her lifetime. This measurement can change depending on the risk factors a person has for the disease. The lifetime risk for women to develop breast cancer is approximately 12 percent.

Liquid biopsy

A liquid biopsy is a sample taken from a person’s non-solid tissue, usually blood. It can be used to identify the presence of cancer cells shed from a tumor (or pieces of DNA from tumor cells) that are circulating in the blood. This type of test has the potential to improve early detection of cancer, track the disease’s progression, and help guide treatment.

Local recurrence

When a patient’s cancer returns in either the region it first appeared or in neighboring lymph nodes it is referred to as local recurrence.

Locally advanced breast cancer

This term describes breast cancer that has spread within the breast or to nearby lymph nodes but has not spread to distant parts of the body (metastatic breast cancer).

Lumpectomy

See breast-conserving surgery.

Lymph nodes

These small, bean-shaped structures belong to the lymphatic system, which is part of the body’s immune system. Lymph nodes (or lymph glands)—found in the underarm, neck, chest, stomach, and groin—remove harmful substances such as bacteria and viruses from the body’s lymphatic fluid. The extent to which breast cancer has spread to nearby lymph nodes plays a role in determining the stage of a person’s disease.

Lymphatic system

This network of tissues and organs protects the body from infection and disease, among other functions. It consists of lymph nodes, lymph vessels, lymph ducts, the thymus gland, bone marrow, and the spleen. Lymph—a watery fluid containing white blood cells—flows through the lymphatic system, maintaining fluid balance and removing waste and harmful substances from the body’s tissues.

Lymphedema

Lymphedema occurs when lymph (the fluid that flows through the lymphatic system) is unable to circulate and builds up in the body’s soft tissues—often in one of the arms or legs—and causes swelling. Other symptoms include a feeling of heaviness or tightness in the affected area, limited range of motion, and achiness. In breast cancer, lymphedema may develop following surgery and can also be a side effect of certain treatments such as radiation therapy. It may develop within days of or even years after treatment.

Male breast cancer

This is a rare cancer that develops in a man’s breast tissue. The exact cause is unknown. Risk factors include family history and gene mutations, high estrogen levels, and exposure to radiation. About 2,600 men are diagnosed with breast cancer each year and roughly 500 die from the disease.

MammaPrint

Used in people with early-stage breast cancer, MammaPrint is a genomic test that helps identify patients whose cancer is at high risk of recurring or spreading to other parts of the body. It analyzes the activity of a group of 70 genes within a tumor and provides a “high risk” or “low risk” score. Physicians use the results to help guide treatment decisions for patients with certain types of breast cancer. BCRF researcher Laura van ‘t Veer, PhD developed the groundbreaking test.

Mammogram

This X-ray of the breast is used to identify changes in breast tissue that may reveal breast cancer or an increased risk of developing breast cancer. It is the primary breast cancer screening method. A mammogram is read by a radiologist.

Margins

A margin is a border of tissue surrounding a breast tumor that is removed along with tumor during breast-conserving surgery. During or after surgery for breast cancer, a pathologist will examine this tissue to check for the presence of breast cancer cells. If none are detected, the margins are said to be clear, and additional surgery usually isn’t necessary. Positive margins, on the other hand, mean cancer cells are present and the patient may require an additional surgery.

Mastectomy

A mastectomy is the surgical removal of one or both breasts. In a partial mastectomy, only a portion of the breast is removed (see breast-conserving surgery). A double mastectomy is the removal of both breasts. Mastectomies are usually performed to treat breast cancer, but some women who have a strong family history of breast cancer or a mutation in the BRCA genes may opt to have a preventive (or prophylactic) mastectomy to reduce their risk of developing the disease.

Metastatic breast cancer

Breast cancer is considered metastatic when it has spread beyond the breast and lymph nodes. Metastatic breast cancer (MBC) is also referred to as advanced breast cancer or stage IV breast cancer. When breast cancer spreads, it most commonly invades the bones, brain, lungs, or liver. At this stage, the disease is incurable. MBC accounts for the majority of breast cancer deaths. However, there are treatments that extend and improve people’s quality of life after an MBC diagnosis. Advanced breast cancer research remains a major area of focus for BCRF.

MicroRNA

MicroRNAs (miRNAs) are short segments of RNA (ribonucleic acid, which is similar to DNA) that circulate in the body. They are an area of interest in breast cancer research because they could potentially serve as biomarkers—meaning they could be used in the diagnosis and prognosis of the disease.

Microtubules

These are structures within a cell that are crucial for its shape and function, and they also play a role in cell division. Chemotherapy drugs such as like Taxol® (paclitaxel) prevent cancer cells from dividing by binding to their microtubules.

Mortality

In medicine, mortality refers to the number of deaths within a certain group of people within a particular period of time.

National Cancer Institute

This federal governmental agency conducts and supports cancer research and training across the United States. The National Cancer Institute (NCI) also provides comprehensive information for the public about different types of cancer.

Neoadjuvant therapy

Neoadjuvant therapies are treatments that are given before the initial treatment of breast cancer (surgery) in order to shrink the tumor. Some examples of neoadjuvant therapy include chemotherapy, radiation therapy, and endocrine therapy.

Observational study

In this type of study, researchers observe individuals or measure certain outcomes in a natural setting (as opposed to a laboratory) without intervening. Observational studies allow scientists to understand the impact of particular risk factors on health outcomes. For example, a researcher might follow a group of women to see if the amount of a particular food they eat has an effect on their risk of developing breast cancer.

Oncogene

Oncogenes are genes that, in their mutated (changed) form, cause uncontrollable cell growth, potentially leading to cancer.

Oncologist

This is a physician who has received special training to diagnose and treat cancer. A medical oncologist is usually the main health care provider for cancer patients. There are also radiation oncologists and surgical oncologists.

Oncotype DX test

This is a type of genomic test that helps determine how likely is it that a patient’s breast cancer will recur (come back) following surgery and if she or he is likely to benefit from chemotherapy. It is used in patients with early-stage, estrogen receptor-positive breast cancer. The Oncotype DX test can also be used in those with ductal carcinoma in situ to help predict the risk of recurrence and help determine whether they may benefit from radiation therapy following a lumpectomy.

p53 gene

This gene functions as a tumor suppressor gene. Mutations in p53 are commonly found in many types of cancer, including breast cancer. It considered a promising target for anti-cancer therapy.

Palbociclib

This drug (brand name: Ibrance®) is used in combination with aromatase inhibitors such as fulvestrant in postmenopausal breast cancer patients who were not previously treated with hormone therapy. Palbociclib is part of a group of drugs called CDK4/6 inhibitors. It works by interrupting signals that stimulate the division and growth of cancer cells. The drug is commonly used to treat hormone receptor–positive and HER2-negative breast cancer that has spread to neighboring or distant tissues. It is administered orally.

Palliative care

Palliative care is a specialized form of medical care for patients living with a serious illness such as breast cancer. The goal is to improve patients’ quality of life by addressing their physical, emotional, social, and spiritual issues. Palliative care specialists also provide support for the patient’s caregivers. Unlike hospice care, which is intended for patients who are terminally ill and nearing the end of their life, palliative care can be administered at any point in a person’s illness, regardless of whether their condition is terminal.

PARP inhibitors

These are drugs that block the function of poly (ADP-ribose) polymerase (PARP), which is a protein that normally helps cells repair DNA damage. Inhibiting PARPs is a method of targeting cancers with defects in DNA repair, such as BRCA1 and BRCA2 mutation-associated breast cancers. When PARP is blocked, it prevents cancer cells from repairing their damaged DNA, which causes them to die.

Pathologic complete response

When a pathologist finds no evidence of cancer in a patient’s tissue samples (removed during surgery or via biopsy) following treatment, the patient is said to have achieved pathologic complete response.

Pathologist

A pathologist is a physician who specializes in the origin, nature, and course of disease. Pathologists are trained to identify and diagnose disease by studying cells and tissues obtained from a surgical procedure or biopsy.

PD-L1

PD-L1—short for “programmed death ligund 1”—is a protein produced by cancer cells that inactivate T-cells, which play a major role in immune response. A promising group of drugs called PG-L1 inhibitors are being developed for cancer patients. They work by blocking PD-L1, thereby boosting the body’s immune response against cancer cells.

Peripheral neuropathy

This is the term for the numbness, weakness, tingling, and pain that results from nerve damage. It typically begins to affect the hands and feet and gets worse over time. Some chemotherapy drugs and other treatments for cancer (radiation therapy, surgery) can cause peripheral neuropathy.

PET scan

Short for “positron emission tomography,” PET scans are a type of imaging test that show how the body’s organs and tissues are working at a cellular level. They are commonly used in breast cancer patients to determine whether the disease has spread to the lymph nodes or other parts of the body.

Placebo

This is substance or treatment that has no therapeutic value. Placebos are used in medical research to compare the effectiveness of new drugs or interventions. For example, a researcher may give one group of study participants a drug and give another group a placebo (such as a sugar pill that resembles the drug) without telling any of the participants whether they’re taking the actual drug or a fake. This approach is useful because people may have expectations about the drug’s efficacy, which can have an impact on results.

Precision medicine

This is an approach to patient care that involves matching the right treatment to the right person at the right time. Precision medicine takes into account a patient’s genes, environment, and lifestyle. It is an emerging field of medical science.

Primary breast cancer

This term describes breast cancer that has not spread beyond the breast or the nearby lymph nodes.

Progesterone

This hormone plays a major role in maintaining women’s reproductive health. Its functions include supporting pregnancy and regulating the menstrual cycle. It is produced by the body, and it can also be produced in a laboratory to treat conditions such as abnormal uterine bleeding. Unfortunately, progesterone can also promote the growth and spread of certain forms of cancer, including breast cancer. Patients whose breast cancer cells have progesterone receptors and are fueled by progesterone are diagnosed with progesterone receptor–positive breast cancer.

Progesterone receptor

The progesterone receptor (PR) is a protein found in and on certain cells in the body that binds to the hormone progesterone. Healthy breast cells have PRs, as do some breast cancer cells. When progesterone binds to certain breast cancer cells, it fuels the growth and spread of breast cancer.

Progesterone receptor–negative

Breast cancer cells that don’t require progesterone to grow and spread are considered progesterone receptor (PR)–negative. These cancer cells have few or no PRs.

Progesterone receptor–positive

Breast cancer cells that have PRs and require progesterone to grow and spread are considered progesterone receptor (PR)–positive.

Progression-free survival

This is the amount of time during and after treatment when a patient lives with a disease, but it does not worsen. In clinical trials, progression-free survival (PFS) is used as a way of evaluating how well a new treatment works.

Proliferation

In the context of cancer, proliferation is used to describe how quickly cancer cells are dividing. If the rate of cancer cell proliferation is high, this means the cancer is fast-growing and more aggressive. A test called Ki-67 measures proliferation rate.

Quality of life

This describes the general wellbeing of a person, and it is an important aspect of cancer care and research. Quality of life means different things to different people; it may encompass a person’s physical health, mental and spiritual wellbeing, sexual function, financial health, and much more. It is a concern for both breast cancer patients and survivors who may be dealing with lingering effects of the disease.

Radiation therapy

Radiation therapy is a form of treatment in which intense beams of X-rays (or gamma rays, neutrons, protons, or other sources) target cancer cells to eradicate them and shrink the size of a tumor. Unlike chemotherapy, which is a systemic treatment, radiation therapy usually only affects the part of the body being treated. It may be administered before surgery (neoadjuvent therapy) or after surgery (adjuvant therapy). Radiation therapy can be given externally (called external beam radiation) or internally, in which a source of radiation is placed inside the body. It can be used alone or in combination with other types of treatment.

Radiologist

A radiologist is a physician who has received training in applying radiation therapy and interpreting X-ray images.

Raloxifene

This medication (brand name: Evista®) is part of a class of drugs called selective estrogen receptor modulators (SERMs). Raloxifene is used to reduce the risk of breast cancer development and to prevent and treat osteoporosis. It blocks estrogen receptor–positive breast cancer growth and prevents breakdown of bone tissue. It is administered orally.

Recurrence

This term is used when cancer comes back after treatment. It may be either a local recurrence (in the same area as the original), regional recurrence (in the lymph nodes or tissues near the breast), or distant recurrence (in other organs or tissues far from the original site). One-third of women will experience a recurrence in their lifetime, so finding ways to prevent recurrence is an important area of study in breast cancer research.

Regional recurrence

When a patient’s cancer returns in neighboring lymph nodes or tissues it is referred to as a regional recurrence.

Relapse-free survival

See disease-free survival.

Remission

This term describes a decrease or lack of signs and symptoms of cancer in the body. There are two types of remission: partial and complete. Partial remission means the tumor is smaller but hasn’t totally disappeared. Complete remission means there is no evidence of cancer in the body; however, it is not synonymous with “cure” because the cancer could recur (come back).

RNA

Like DNA, ribonucleic acid (RNA), is a type of nucleic acid. Unlike DNA, RNA comes in three different types—ribosomal, transfer, and messenger—that serve a variety of functions in the cells. RNA pays a major role in regulating and expressing genes.

Sentinel lymph node biopsy

This procedure is used to determine whether breast cancer has spread from the primary tumor into the lymphatic system. A surgeon removes the sentinel node(s), which is the first node (or group of nodes) into which cancer cells are likely to spread. A pathologist will then check the node(s) for the presence of cancer cells. A sentinel lymph node biopsy (SLNB) is usually conducted at the same time the primary tumor is removed.

Somatic

This term is used to describe anything that has to do with the body. All of the cells in the body are considered somatic cells, with the exception of the reproductive (germ) cells. In the context of breast cancer, you may see references to “somatic mutations,” which are mutations (changes) in somatic cells that do not affect offspring. (Mutations that affect the germ cells are called germline mutations.)

Stage

The stage of a person’s cancer is used to help determine the best treatment options, predict the outcome of the disease, and so forth. It is based on the size, severity, and other characteristics of the cancer. Stages range from 0 (non-invasive cancer) to IV (invasive cancers that have spread from the breast to other parts of the body, also known as metastatic breast cancer).

Stereotactic radiosurgery

This non-surgical procedure uses multiple radiation beams to treat tumors, as well as other medical conditions. The beams are precisely targeted to damage the DNA of cancer cells in a specific region without harming healthy tissue.

Stroma

Stroma describes the supportive tissue of an organ or other structure in the body (such as glands). Tumors also have stroma, which supports the tumor by supplying it with nutrients and removing waste products.

Survival rates

Given a certain period of time after diagnosis, survival rate is defined as the percentage of people in a particular treatment group who are alive for that specific time period. For example, the five-year breast cancer survival rate is 90 percent, meaning that 90 percent of people survive five years after their diagnosis.

Systemic treatment

This describes therapies in which a drug is spread throughout the body. This is in contrast to localized treatments such as radiation therapy that target a specific part of the body. Examples of systemic treatments for cancer include chemotherapy, hormone therapy, and immunotherapy.

Tamoxifen

This anti-estrogen drug is used in both men and women to shrink hormone receptor–positive tumors and reduce the risk of the cancer coming back or developing in the other breast. Tamoxifen may also be given as a preventive measure to women who have not been diagnosed with breast cancer but are at a high risk of developing the disease. It is administered orally.

Taxanes

These are chemotherapeutic drugs to treat cancer. They work by inhibiting mitosis (the process of cell reproduction), which halts cell division in tumors. Taxol® is an example of a taxane.

Taxol®

Taxol® (generic name: paclitaxel) is a type of chemotherapy drug that reduces the risk a cancer will recur (come back) and blocks the growth of cancer cells. It is administered intravenously.

TNM staging system

This staging system, which stands for tumor/node/metastasis (TNM) is a method of classifying a tumor by its size, whether the cancer has affected the lymph nodes, and if the cancer has metastasized (spread). It is used to determine prognosis and guide treatment decisions.

Tomosynthesis

In this X-ray technique, several images of the breasts are taken and then sequenced to create a 3-D image of the breast. Tomosynthesis is used to detect breast cancer early, which is when it is more treatable. It also referred to as 3D mammography.

Toxicity

This term is used to describe the extent to which a therapy or drug produces harmful side effects.

Triple-negative breast cancer

This form of breast cancer (often shortened to TNBC) is estrogen receptor–negative, progesterone receptor–negative, and HER2–negative. This means the cancer does not need hormones to grow, and the cancer cells have few or no HER2 receptors. TNBC is an aggressive form of breast cancer, and it is more likely to recur than other forms of the disease.

Tumor

A tumor is an abnormal growth of cells that serves no function in the body. It may be malignant (cancerous) or benign (non-cancerous).

Tumor microenvironment

This refers to the normal cells, blood vessels, and signaling molecules that surround and feed a tumor. The tumor microenvironment (TME) can carry out tumor-promoting functions that affect how the tumor grows and spreads. In cancer research, it is considered to be a promising treatment target.

Tumor suppressor gene

The normal function of a tumor suppressor gene is to block processes that promote cell growth and cancer development. Mutations (changes) to this class of genes can alter the genes’ normal functions and may lead to cell proliferation (a rapid increase in the number of cells) and tumor development.

Tumorigenesis

This describes the production or formation of tumors.

Whole genome sequencing

In this process, a person’s entire genome is analyzed. Identifying certain mutations (changes) or patterns in the genome can help characterize mutations that influence cancer development.

Breast Cancer Glossary