Breast cancer is a type of cancer that usually forms in the ducts or lobules of the breast. Lobules are the glands that produce milk, and ducts are the tubes that transport milk to the nipples.

As of January 2021, over 3.8 million women in the United States have a history of breast cancer. It’s estimated that there will be another 281,550 new cases of breast cancer this year.

Male breast cancer is less common, but about 2,550 men were diagnosed with invasive breast cancer in the United States in 2018.

In this article, we’ll highlight the most important facts you should know about breast cancer.

There are many types of breast cancer. Here are the most common forms.

In situ breast cancer

Breast cancer is classified as in situ when it’s contained to the milk ducts or glands and hasn’t spread to other breast tissue. Within this class, there are a few different types.

Ductal carcinoma in situ

Ductal carcinoma in situ is when cancer is limited to the ducts of your breasts. It makes up about 1 in 5 cases of breast cancer in the United States.

About 20 to 53 percent of women with ductal carcinoma in situ develop invasive breast cancer.

Lobular carcinoma in situ

Lobular carcinoma in situ is an uncommon condition characterized by abnormal cells in the glands that produce milk. It’s considered a benign condition, but it increases your risk of some types of breast cancer later on.

It’s important to note that lobular carcinoma in situ often doesn’t show up on mammograms.

Invasive breast cancers

Invasive breast cancer occurs when cancer cells spread from the ducts and glands into your breast’s fat or connective tissue.

Invasive ductal carcinoma

Invasive ductal carcinoma is the most common type of breast cancer and makes up about 50 to 70 percent of breast cancers. It occurs when cancer cells spread from your milk ducts into the surrounding breast tissue. If not caught early, it can potentially spread to other parts of your body through the lymphatic system.

Invasive lobular carcinoma

Invasive lobular carcinoma makes up about 10 percent of breast cancers. About 1 in 5 women have it in both breasts.

Invasive lobular carcinoma tends to be harder to detect than invasive ductal carcinoma. It occurs when cancer begins in the glands that produce milk and spread to nearby tissue. It also has the potential to spread to distant parts of your body if not treated early.

About 1 in 8 women in the United States develop invasive breast cancer at some point in their life. About 1 in 1,000 men in the United States will also experience breast cancer.

It’s projected that there will be 281,550 new breast cancer cases in 2021 and 43,600 deaths. The 5-year relative survival rate is 90.3 percent. Relative 5-year survival rate is a measure of how many people are still alive 5 years after their diagnosis compared to people in the general population of the same age and sex.

According to data from the National Cancer Institute, the death rate for breast cancer has decreased every year since 1988, while the number of new cases each year has stayed about the same.

Breast cancer by state

According to data from the Centers for Disease Control and Prevention (CDC), the states with the highest rates of breast cancer are:

StateAge-adjusted rate per 100,000 women each year
District of Columbia145.9
New Jersey138.4

The states with the lowest breast cancer rates are:

StateAge-adjusted rate per 100,000 women each year

Breast cancer by ethnicity

Breast cancer rates vary between ethnic groups in the United States.

EthnicityRates per 100,000 women per year
Non-Hispanic white128.1
African American124.3
Native American/Alaska Native91.9
Asian American/Pacific Islander88.3

Researchers still don’t fully understand why breast cancer develops in some people but not others. However, a number of risk factors have been identified.

Sex and age

People assigned female sex at birth have a much higher chance of developing breast cancer than males. Your chances of developing breast cancer also increase with age.

In 2016, approximately 99.3 percent of breast cancer cases occurred in women over age 40, and 71.2 precent occurred in women over age 60.

Family history

Nearly 25 percent of breast cancer cases are linked to family history. Women with a first-degree relative with breast cancer have a 1.75-fold higher chance of developing breast cancer than women who don’t have an affected close relative.

Reproductive factors

Starting menstruation before age 12 or menopause after age 55 is linked to an increased risk of developing breast cancer due to an increased amount of time exposed to elevated estrogen levels.

Having your first pregnancy after age 30, never having a full-term pregnancy, and not breastfeeding are also linked to an increased risk of developing breast cancer.

Breast density

If you have an increased amount of glandular and connective tissue in your breasts, it can be more difficult to identify cancer cells in a mammogram. This increases the chances that breast cancer may go undetected.

About 36 percent of women in the United States between the ages of 40 to 74 have dense breasts.

Exposure to estrogen

Using birth control pills is linked to an increased risk of developing breast cancer due to the increased exposure to estrogen. However, these hormones don’t increase your risk once you’ve stop using them for more than 10 years.

Hormone replacement therapy is also thought to increase the risk of developing breast cancer in women.

Other factors

According to the CDC, lifestyle factors may increase your chances of developing breast cancer, including:

  • lack of regular exercise
  • being overweight or obese after menopause
  • frequent alcohol consumption

and possibly:

  • smoking
  • exposure to cancer-causing chemicals
  • working a night-shift job

Know the symptoms

Breast cancer symptoms vary between people, and some may not have any noticeable signs. Experiencing one of the following symptoms doesn’t necessarily mean you have breast cancer, but it does indicate that you should visit a doctor for an examination:

  • lump in your breast or armpit
  • pain or swelling in your breast
  • irritation or dimpling
  • redness or flaking skin
  • changes in the size or shape of your breast
  • discharge from your nipple (other than breast milk)
  • pain around your nipple
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Damage to the DNA of healthy cells can lead cancer cells to form. These cells rapidly divide and can develop into tumors. It’s still not clear why some people develop breast cancer while others do not. However, a combination of genetic and environmental factors are thought to play a role.

Genetic factors

About 5 to 10 percent of breast cancers are caused by gene mutations inherited from a parent. Two of the most common mutations are changes in the BRCA1 and BRCA2 genes. According to recent statistics, women with a BRCA1 mutation have a 55 to 65 percent chance of developing breast cancer during their lifetime, while those with the BRCA2 gene have a 45 percent lifetime risk.

According to the National Cancer Institute, the 5-year relative survival rate for breast cancer in women is about 90.3 percent. The survival rate is highest when cancer is detected in the early stages.

By stage, the 5-year relative survival rates are:

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

The American Cancer Society lists the 5-year relative survival rate as 84 percent for men.

Survival rate by ethnicity

According to the CDC, the death rate per 100,000 cases is:

EthnicityDeaths per 100,000 people
Non-Hispanic white19.4
Black/African American26.9
Native American/Alaska Native11.5
Asian American /Pacific Islander11.9

Black women have the highest death rate from breast cancer. It’s thought that this may in part be due to socioeconomic factors that lead to fewer Black women receiving timely treatment.

Other breast cancer facts

Here are some other facts to know about breast cancer:

  • Aside from skin cancer, breast cancer is the most common cancer in the United States.
  • Breast cancer is the second most common cause of cancer death in women behind lung cancer.
  • The death rate of breast cancer declined by 39 percent between 1989 to 2015 in the United States.
  • Risk factors for the development of breast cancer in men include exposure to radiation, obesity, mutation in the genes BRCA 1 and 2, a family history of breast or ovarian cancer, Klinefelter syndrome, testicular disorders, diabetes, and gynecomastia.
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Breast cancer is the second most common cause of female cancer death in the United States. Nearly 1 in 8 women will experience invasive breast cancer at some point in their life.

Researchers still don’t know why some people develop breast cancer and others don’t, but certain risk factors are known to increase your chances, such as certain gene mutations, delayed menopause, and use of hormonal birth control.

The United States Preventive Services Task Force recommends women ages 50 to 74 receive a mammogram once every 2 years to screen for breast cancer. Detecting breast cancer in the early stages — before it spreads to other parts of your body — gives you the best outlook.