What Is Breast Cancer?

Updated on Sep 11, 2023 at 4:05 PM

Photo Illustration by Keila Gonzalez

This informational guide, part of POPSUGAR's Condition Center, lays out the realities of this health concern: what it is, what it can look like, and strategies that medical experts say are proven to help. You should always consult your doctor regarding matters pertaining to your health and before starting any course of medical treatment.

Breast cancer affects millions of people worldwide, from those who personally experience the disease to their loved ones and caretakers. According to the CDC, about 264,000 women and 2,400 men are diagnosed with breast cancer every year in the US, and it remains the most common type of cancer in women, aside from skin cancer.

A diagnosis of any kind of cancer is often overwhelming and confusing. But the American Cancer Society reports that due to improvements in treatment, early detection, and increased awareness, the fatality rates of breast cancer have continued to decrease in women over 50, and there are over 3.8 million breast cancer survivors in the United States alone — a testament to how important it is to stay educated on the causes, symptoms, and available treatments.

Understanding Breast Cancer

Breast cancer is a type of cancer that starts in one or both breasts, according to the American Cancer Society. The ACS site notes that the cancer can spread "when the cancer cells get into the blood or lymph system and then are carried to other parts of the body."

Very often, people who have undiagnosed breast cancer don't notice pain or any other symptoms, says Samuel Wong, MD, board-certified ob-gyn of New Hope Fertility. However, some people may experience swelling of the breast, armpit, or collarbone, skin dimpling (when the skin thickens or feels like an orange peel), or nipple retraction, redness, thickening, or discharge.

Others might notice breast discomfort or discover a breast mass — or lump — via self-examination or during a routine screening like a mammogram, which is a specialized type of X-ray for the breast. A lump does not automatically mean you have cancer (a cyst, for example, can result in a benign lump), but the American Cancer Society urges you to see your doctor right away if you find a new lump or experience any of the above symptoms.

Types of Breast Cancer

There are several different kinds of breast cancer, which are categorized by how they develop, where they begin, and how much the cancer has spread. In general, there are two main types of breast cancer: invasive and noninvasive.

Invasive breast cancer means the cancer has spread to other parts of the breast:

Invasive ductal carcinoma. This type of cancer starts in the breast ducts (also called the "milk ducts," this is the tube that carries milk to the nipples) and can go on to spread to other parts of the breast tissue. According to the American Cancer Society, about 80 percent of all invasive breast cancers are IDC.
Invasive lobular carcinoma. This type of cancer begins in the lobules (the gland that produces milk) and can go on to spread to close-by breast tissue. Alongside invasive ductal carcinoma, this is one of the most common forms of breast cancer, per the CDC.
Triple-negative. Another type of invasive breast cancer, the triple-negative name refers to a particular type of cancer cell, which tests negative for estrogen and progesterone receptors, as well as HER2 protein. Triple-negative cancers are more common in people under 40, Black women, and those who have a BRCA1 mutation, per the American Cancer Society.
Metastatic breast cancer. Metastatic breast cancer, sometimes called stage 4 breast cancer, means the cancer has metastasized (spread) to other parts of the body, according to the Cleveland Clinic. Sometimes, the cancer can spread as far as the bones, lungs, liver, or brain. For some, the breast cancer is detected at the metastatic stage, or for others, the breast cancer may come back as metastatic.
Inflammatory breast cancer. This is a rare form of breast cancer, affecting about one percent to five percent of those diagnosed with breast cancer, according to the American Cancer Society. IBC is an aggressive form of breast cancer and can be difficult to diagnose because it typically does not cause a lump and may not show up on a mammogram, the society reports. IBC is also more common in Black women, people under 40, and those who are overweight.
Recurrent breast cancer. Like the name suggests, recurrent breast cancer recurs, or comes back, months or years after initial treatment. In some cases, the breast cancer has a local recurrence (it comes back to the same place or breast), a regional recurrence (a nearby area of the body), or distant recurrence (meaning the cancer has metastasized to another part of the body.)

Noninvasive breast cancer (sometimes called in situ or pre-cancer) means the cancer has not spread into other areas. There are two main types:

Ductal carcinoma in situ. DCIS is a type of breast cancer in the milk ducts that has not spread to the surrounding tissue. DCIS can develop into an invasive breast cancer and usually requires treatment.
Lobular carcinoma in situ. LCIS is a cancer that started in the lobules but has not spread to surrounding tissue. However, LCIS isn't a true cancer and is considered benign. According to Mayo Clinic, LCIS does mean you are more likely to develop a "true" breast cancer, and more regular screenings and observation may be necessary.

Causes of Breast Cancer

At its core, cancer is the uncontrolled growth of cells. For breast cancer, this cell growth occurs in the breast, resulting in malignant tumors. There are certain risk factors that may increase one's likelihood of breast cancer, including:

Genetics. It's estimated that "5 to 10 percent of breast cancers are linked to gene mutations passed through generations of a family," states the Mayo Clinic. Some of the most-talked-about genes are the breast cancer gene 1 (BRCA1) and breast cancer gene 2 (BRCA2). These can increase your risk of breast and ovarian cancer. But genetic risk doesn't guarantee you will get breast cancer; lifestyle can also play a role.
Age. The risk for breast cancer increases with age, according to the CDC. Most breast cancers are diagnosed after age 50. "The longer we live, there are more opportunities for genetic damage (mutations in the body)," according to the nonprofit Breastcancer.org.
Hormones. Specifically, the sex hormones estrogen and progesterone. "Being exposed [to estrogen and progesterone] for a long time and/or to high levels of these hormones has been linked to an increased risk of breast cancer," according to the National Cancer Institute. (The growth of some breast cancer cells that make up what's known as hormone receptor-positive tumors are specifically triggered by these two hormones, while the growth of hormone receptor-negative tumors are not.) That's why research has indicated that people who started menstruating before age 12 may be at increased risk for breast cancer — because of an earlier exposure to estrogen. "The earlier a woman starts having periods, the longer her breast tissue is exposed to estrogens released during the menstrual cycle. This means a greater lifetime exposure to estrogen," states breast cancer organization Susan G. Komen For the Cure.
Alcohol use. In analyzing the data from 53 studies researchers found that a person's relative risk of breast cancer increased by about seven percent for each alcoholic drink they consumed daily. According to the American Cancer Society, alcohol can also increase your estrogen levels in the body, which may explain why.
Race. According to Cleveland Clinic, non-Latinx white women have a higher risk of developing breast cancer when compared to women of other races or ethnicities, but Black women are almost as likely to develop the cancer. Black women are also more affected by aggressive subtypes of breast cancer, such as triple-negative breast cancer (TNBC). Economic and social disparities also come into play: the mortality rate of Black women is 40 percent higher compared to white women, and Black women are more likely to have no insurance or insufficient coverage, limiting access to mammography screening and impacting options for therapeutics. Asian, Latinx, and Native American women are the least likely to develop breast cancer, per Cleveland Clinic.

The Most Effective Breast Cancer Treatment

There are many options for breast cancer treatment including surgery, chemotherapy, radiation treatment, and hormone therapy. The survival rates for those with breast cancer are encouraging. Five-year survival rates range from 99 percent for localized cancer (where cancer is only in the breast) to 86 percent for regional (cancer has spread outside the breast to nearby areas) — meaning with treatment, the majority of people have a good prognosis. But once the cancer has spread to distant parts of the body, such as the liver or lungs, the five-year survival rate drops to 29 percent, which is why experts emphasize sticking to a regular screening schedule as recommended by your doctor and organizations such as the US Preventive Task Force to help catch any potential cancers as early as possible. Dr. Wong says that people are recommended to begin having mammograms at age 40, for instance; although a strong family history for the disease or other risk factors may prompt your doctor to suggest earlier screenings.

The American Cancer Society says treatment can be localized (just treating the tumor) or systemic (treating all cancer cells in the body). Localized treatment may include surgery or radiation, while systemic may involve chemotherapy, hormone therapy, targeted drug therapy, or immunotherapy.