Breast cancer

Breast cancer is a type of cancer that starts in the breast tissue. It can cause signs like finding a lump in the breast or noticing changes in the breast’s shape.

Several things can increase the chance of developing breast cancer, such as obesity, not exercising enough, drinking alcohol, or getting older. Some people are at higher risk because of family history or certain genes.

To confirm if someone has breast cancer, doctors take a biopsy of the suspicious tissue.

Screening for breast cancer is important because finding it early often leads to better outcomes. There are different ways to screen, and doctors are still studying them.

When breast cancer is found, treatments may include surgery, radiation therapy, chemotherapy, hormonal therapy, and targeted therapy.

Overall, many people with breast cancer can live long lives. Breast cancer is the most common type of cancer in women. It is far more common in women than in men.

Signs and symptoms

Most people with breast cancer do not feel any signs when it is first found; a test during a screening shows the growth. When signs are present, a new lump in the breast is the most common sign. Many breast lumps are not cancerous, but lumps that are painless, hard, and have uneven edges are more likely to be cancerous. Other signs include the skin of the breast feeling thicker or looking like orange peel, swelling or pain in the breast, dimpling, redness, or dryness of the breast skin, and pain or the nipple turning inward. Some people may notice unusual fluid coming from the breasts or swelling of the small parts under the arms or along the collar bone.

Some rarer types of breast cancer cause special signs. A type where the growth blocks the small tubes in one breast can make the breast swell a lot and turn red over a few months. Another type can cause red, scaly irritation on the nipple and the area around it.

When the growth grows larger, it can spread to other parts of the body, most often to the bones, liver, lungs, and brain. In the bones, this can cause swelling and pain. In the liver, it can cause pain in the belly and feeling sick. In the lungs, it can cause trouble breathing. In the brain, it can cause headaches and trouble speaking or seeing.

Screening

Breast cancer screening means checking women who don’t have symptoms to find tumors early, when they are easier to treat. The most common test is called a mammogram, which uses a low-dose X-ray to take pictures of the breast. During this test, each breast is gently pressed between two plates. Tumors can show up as unusual shapes or small spots called microcalcifications in the images.

Mammograms can also show how dense the breast tissue is. Dense tissue can make it harder to see tumors. There are different ways to check for breast cancer, such as ultrasound, magnetic resonance imaging (MRI), or tomosynthesis, especially for women with very dense breasts.

Regular mammograms help lower the chances of dying from breast cancer. Many medical guidelines suggest women aged 50–70 get a mammogram every year. Some guidelines also recommend this for women aged 40–49. For women at higher risk, adding MRI to mammography can help find dangerous tumors earlier. Checking your own breasts for lumps does not lower the risk of dying from breast cancer. While clinical exams by a health professional are common, it is not known if they reduce the risk of dying from breast cancer. Screening is common in many wealthy countries but less so in poorer ones.

However, mammograms are not perfect. They can miss some breast cancers and sometimes give false-positive results, which can cause worry and lead to extra tests like biopsies.

Diagnosis

If a lump or change in the breast is found during a mammogram or exam, more tests are done to learn more about it. This usually means another mammogram and an ultrasound. A small sample of tissue, called a biopsy, is taken to check if the lump is cancer. Most lumps are not cancer but are changes in the breast tissue.

Breast cancers can be different types based on where they start. The most common type starts in the tubes that carry milk. Doctors also look at how fast the cancer cells are growing to help decide how to treat it. This information helps doctors plan the best care.

Management

The way doctors treat breast cancer depends on the person's health, the type of cancer, and how far it has spread.

If the cancer has not spread beyond the breast, doctors often remove the tumor and some surrounding tissue. They try to keep as much healthy breast as possible. This can be done by removing just the tumor (lumpectomy) or a larger part of the breast (partial mastectomy). Sometimes, the whole breast needs to be removed (full mastectomy). To help prevent the cancer from spreading, doctors may also remove nearby lymph nodes using a procedure called sentinel lymph node biopsy.

After surgery, many people get radiotherapy to lower the chance of the cancer coming back. Radiation may be aimed at the whole breast or just the scar and chest wall. Radiation is usually given several times a week for several weeks. Some people also have a procedure called brachytherapy, where a small device with radioactive material is placed near the tumor site.

Chemotherapy can also help lower the chance of cancer returning. It is usually given in cycles over several months. Different drugs are used depending on the person's health and the type of cancer.

For people whose cancer makes too much of a certain protein (HER2-positive), special drugs like trastuzumab can help treat the cancer.

After chemotherapy, some people benefit from endocrine therapy, which lowers the amount of certain hormones that some breast cancers need to grow. This treatment is usually given for several years.

Prognosis

Breast cancer outcomes can vary a lot depending on where you live and how far the disease has spread when it is found. In many places, most women live for several years after being diagnosed.

How far the cancer has spread when it is found is very important. Women whose cancer is only in the breast often have the best outcomes. For those whose cancer has spread to other parts of the body, the chances are lower.

Risk factors

Main article: Risk factors of breast cancer

Many things can affect the chance that someone might develop breast cancer. One big factor is related to a woman's body and hormones. Women who start their periods very early or go through menopause later may have a higher chance of getting breast cancer.

Having a baby at a younger age can lower the risk, but this protection gets smaller the older a woman is when she has her first child. Breastfeeding can also lower the risk a little bit for each year a baby is breastfed. Certain treatments for menopause symptoms can raise the risk, depending on what kind is used and for how long.

Other factors include lifestyle choices. Drinking alcohol, even in small amounts, can increase the risk. Being overweight or having diabetes can also raise the chance of developing breast cancer. Smoking and not getting enough exercise are also linked to a higher risk. Some genes can play a role too. Women with certain gene changes, like in the BRCA genes, have a much higher chance of getting breast cancer. Other health conditions and past radiation exposure to the chest can also affect risk.

Pathophysiology

See also: Carcinogenesis

Breast cancer happens when cells in the breast grow in an uncontrolled way. There are three main types of breast cancer. The most common type is called hormone receptor-positive. Another type is called triple-negative, and the third is ERBB2-positive. Hormone levels, especially estrogen, can affect how breast cells grow. When estrogen is not balanced, it can cause cells to grow too fast. This growth can turn normal cells into cancer cells.

Like other cancers, breast cancer occurs when normal cells lose their ability to stop growing and stay in place. Some important pathways that normally help cells self-destruct can become stuck due to changes in the genes, which helps cancer cells survive. Certain genes, when changed, can also make cancer more likely.

Prevention

Women can help lower their chances of getting breast cancer by staying at a healthy weight, cutting down on alcohol, and getting more exercise. Even simple activities like brisk walking can help at any age.

Doctors suggest eating lots of vegetables, fruits, whole grains, and beans. Foods with soluble fiber, citrus fruits, omega-3 fats found in fish, and soy products may also help lower the risk. Certain medicines can help lower risk for some women, but they come with other health considerations.

Epidemiology

Main article: Epidemiology of breast cancer

Breast cancer is the most common type of cancer in women in many countries. It makes up about 30% of all cancers in women.

The chances of getting breast cancer differ around the world. In wealthier countries, about 1 in 12 women may develop breast cancer during their lives. In countries with fewer resources, it’s about 1 in 27. This difference is mostly because women in wealthier countries often start having their periods earlier and have children later, which can raise the risk. Also, in lower-income countries, there is less access to checking for breast cancer early and treatments.

Breast cancer mostly affects women, with fewer than 1% of cases happening in men. Women can develop it as young as their teenage years, but the chance grows with age. Most cases happen in women older than 50 years old.

History

Breast cancer has been known for thousands of years. The oldest known case was found in Egypt, dating back over 4,200 years. Ancient doctors described changes in the breast, such as lumps or sores, and tried many treatments, but often felt there was no cure.

Over time, ideas about what caused breast cancer changed. Some thought it was due to imbalances inside the body. In the past, doctors sometimes removed the entire breast to try to stop the disease.

In more recent times, doctors have found better ways to treat breast cancer. They now use different surgeries that save more of the breast and combine them with other treatments. This has led to better care and more hope for those affected.

Society and culture

See also: Breast cancer awareness, List of people with breast cancer, and Cultural differences in breast cancer diagnosis and treatment

In the past, people did not talk much about breast cancer. Now, more people speak about it and look for help. Groups formed to support women with breast cancer in the 1930s and 1940s. In the 1980s and 1990s, more people talked about it as part of movements for women’s rights.

Pink ribbon

Main article: Pink ribbon

The pink ribbon is a symbol for breast cancer awareness. People wear pink ribbons to show support for those affected by breast cancer. Many companies used pink ribbons in the 1990s to raise money for breast cancer. Some people think that wearing a pink ribbon is not enough to solve the problem.

Health disparities in breast cancer

Breast cancer is the most common cancer among women in the United States, and it affects women from all backgrounds. However, some groups face challenges in getting diagnosed and treated.

For example, Black women are often diagnosed with breast cancer at a younger age than white women. This can be due to differences in healthcare access, money, and where they live. Getting regular check-ups and screenings is important to find breast cancer early, when it is easier to treat. Unfortunately, some women, especially those with lower incomes, are less likely to get these screenings, which can lead to later diagnoses.

Efforts to improve access to care, like helping with language barriers, providing transportation, and using mobile clinics, can help. Including people from all backgrounds in research also helps doctors understand breast cancer better and develop better treatments for everyone.

Special populations

Breast cancer is rare in men but can happen. It usually shows up as a lump in the breast. Men with certain health conditions or genetic changes may have a higher chance of getting it. Treatment often includes surgery and sometimes radiation.

Diagnosing breast cancer during pregnancy can be tricky because pregnancy changes can hide the signs. Doctors use the same tests as for others, but they avoid certain X-rays. Some treatments are put off until after the baby is born, and breastfeeding may not be possible if certain medicines are used. The outlook for pregnant women with breast cancer is usually similar to others of the same age.

Research

Scientists work to find new ways to treat breast cancer. They test new medicines and different treatments. They study special treatments that target cancer cells, vaccines, and treatments that change genes.

Each year, meetings happen where researchers share their newest ideas. These meetings help doctors choose the best treatments.

Some studies look at ways to lower the chance of getting breast cancer. For example, a medicine called fenretinide is being tested to see if it can help prevent breast cancer. Doctors also study how to use antibiotics before surgery to prevent infections.

Cryoablation, a method that uses very cold temperatures, is being tested as a possible treatment for small breast cancers. It might be an option for people who cannot have surgery.

Much of what we know about breast cancer comes from studying cells taken from tumors. These cells help scientists understand how breast cancer grows. The first breast cancer cell line was created in 1958, and since then, scientists have created about 100 different cell lines to study. Many of these cell lines come from cancers that have spread beyond the breast.

Other animals

Breast cancer can also happen in animals besides humans. Some animals can get conditions called mammary tumors. Scientists use special mice to study how breast cancer spreads.

Mammary tumor for breast cancer in other animals
Mouse models of breast cancer metastasis