Breast Cancer

Breast cancer happens when cells in the breast tissue grow out of control and form tumors. It is one of the most common cancers affecting women worldwide, though men can develop it too. While a breast cancer diagnosis can be overwhelming, advances in early detection and treatment have led to improved survival rates and better outcomes for many people.

Table of contents

• What is breast cancer?
• Types of breast cancer
• Who is affected by breast cancer?
• Signs and symptoms
• Risk factors
• How is breast cancer diagnosed?
• Treatment options
• Living with and after breast cancer
• Reducing your risk

What is breast cancer?

Breast cancer is a disease in which cells in the breast tissue change and grow out of control, forming tumors^[1]. The breast is made up of sections called lobes, which contain smaller parts called lobules that produce milk. Thin tubes called ducts carry milk from the lobules to the nipple. The breast also contains fatty tissue, blood vessels, and lymph vessels that carry lymph fluid to small bean-shaped structures called lymph nodes^[9].

If left unchecked, breast cancer tumors can spread throughout the body and become fatal^[4]. About 80% of breast cancer cases are invasive, meaning the tumor may spread from the breast to other areas of the body^[1]. Cancer cells can spread into nearby breast tissue and to nearby lymph nodes, or they can metastasize (spread) to other organs. Metastasis can be life-threatening and fatal^[4].

• Breast tissue
• Milk ducts
• Lobules (milk-producing glands)
• Lymph nodes
• Lymph vessels

Types of breast cancer

Healthcare providers identify different types and subtypes of breast cancer so they can tailor treatment to be as effective as possible. The most common type is invasive ductal carcinoma (IDC), which starts in the milk ducts and spreads to nearby breast tissue. This accounts for about 70% to 80% of all breast cancer cases in the United States^[1]. The second most common type is lobular breast cancer, which begins in the milk-producing glands and often spreads to nearby breast tissue. It makes up 10% to 15% of all breast cancer cases^[1].

Ductal carcinoma in situ (DCIS) is breast cancer that starts in the milk ducts but doesn’t spread beyond them. Unlike invasive ductal carcinoma, DCIS is considered an early form that has not invaded surrounding tissue^[1].

Less common types include triple-negative breast cancer (TNBC), which is invasive and spreads more quickly than other breast cancers; inflammatory breast cancer (IBC), a rare and fast-growing cancer that looks like a rash on the breast; and Paget’s disease of the breast, which affects the skin of the nipple and may look like a rash. Paget’s disease accounts for less than 4% of all breast cancers^[1].

Healthcare providers also classify breast cancer by receptor status. Receptors are protein molecules on cell surfaces that can attract or attach to certain substances in the blood, including hormones like estrogen and progesterone. These hormones help cancerous cells grow^[1]. Breast cancers can be:

• ER-positive (ER+): Have estrogen receptors
• PR-positive (PR+): Have progesterone receptors
• HR-positive (HR+): Have both estrogen and progesterone receptors
• HR-negative (HR-): Don’t have estrogen or progesterone receptors
• HER2-positive (HER2+): Have higher than normal levels of the HER2 protein, which helps cancer cells grow. About 15% to 20% of all breast cancers are HER2-positive^[1]

Who is affected by breast cancer?

Breast cancer typically affects women age 50 and older, but it can also affect women who are younger than 50. Men may also develop breast cancer, though this is rare. Approximately 0.5 to 1% of breast cancers occur in men^[1][4]. Everyone is born with some breast tissue, so anyone can get breast cancer^[2].

After skin cancer, breast cancer is the most common cancer diagnosed in women in the United States^[2]. In 2022, there were an estimated 2.3 million women diagnosed with breast cancer and 670,000 deaths globally. Breast cancer occurs in every country of the world in women at any age after puberty, but with increasing rates in later life^[4].

Female gender is the strongest breast cancer risk factor. Roughly half of all breast cancers occur in women with no specific risk factors other than sex and age^[4]. Global estimates reveal striking differences in the breast cancer burden according to human development. In countries with a very high Human Development Index, 1 in 12 women will be diagnosed with breast cancer in their lifetime and 1 in 71 women die of it. In contrast, in countries with a low Human Development Index, while only 1 in 27 women is diagnosed with breast cancer in their lifetime, 1 in 48 women will die from it^[4].

Signs and symptoms

Breast cancer may not cause noticeable symptoms in its early stages. In Western countries, screening programs have succeeded in identifying most breast cancers through screening rather than due to symptoms. However, in much of the developing world, a breast mass or abnormal nipple discharge is often the presenting symptom^[5].

When breast cancer does cause symptoms, they may include^[1]:

• A change in the size, shape, or contour of the breast
• A mass or lump, which may feel as small as a pea
• A lump or thickening in or near the breast or in the underarm that persists through the menstrual cycle
• A change in the look or feel of the skin on the breast or nipple. The skin may look dimpled, puckered, scaly, or inflamed. It may look red, purple, or darker than other parts of the body
• Changes to the nipple

Breast cancer can affect the breasts in different ways. Some breast cancer symptoms are very distinctive, while others may simply seem like areas of the breast that look very different from any other area^[1].

Risk factors

Several factors are associated with an increased risk of developing breast cancer. Some of these risk factors cannot be changed, such as sex, age, family history, and genetics. However, lifestyle choices can also play a role^[5].

Age is an important factor, as the risk of breast cancer continues to increase with age^[5]. A family history of breast cancer and inherited gene mutations also increase risk. Breast cancer is sometimes caused by inherited gene mutations (changes)^[9].

According to a 2017 study by the American Cancer Society, nearly 42% of cancer diagnoses and 45% of deaths in the United States are linked to controllable risk factors for cancer. For breast cancer specifically, the American Cancer Society estimates that about 30% of postmenopausal breast cancer diagnoses are linked to modifiable risk factors^[22].

How is breast cancer diagnosed?

Breast cancer diagnosis often begins with an exam and a discussion of symptoms. During a clinical breast exam, a healthcare professional looks at the breasts for anything that’s not typical, such as changes in the skin or nipple. The health professional also feels the breasts for lumps and checks along the collarbones and around the armpits for lumps^[8].

A mammogram is an X-ray of the breast tissue commonly used to screen for breast cancer. If a screening mammogram finds something concerning, additional imaging tests may be needed^[8].

Other imaging tests used to look at breast tissue include breast ultrasound and breast MRI (magnetic resonance imaging)^[8]. These tests create detailed pictures of the breast to help identify any abnormalities.

To confirm whether cancer is present, a sample of tissue is removed from the breast for testing. This procedure is called a biopsy. A core needle biopsy uses a long, hollow tube to obtain a tissue sample. The sample is sent to a lab for testing by doctors called pathologists, who specialize in examining blood and body tissue^[8].

If cancer is found, additional tests are done to study the cancer cells and determine characteristics such as hormone receptor status, HER2 status, and the cancer’s stage. These factors help healthcare providers plan the most effective treatment^[9].

Treatment options

Treatment for breast cancer combines several approaches and is based on the person, the type of cancer, and how far it has spread^[4]. People with breast cancer often receive more than one kind of treatment^[10].

Surgery is the main treatment for breast cancer and is often the first step. Most people begin their breast cancer treatment with surgery^[14]. There are different types of surgery, including lumpectomy (removing the tumor and some surrounding tissue) and mastectomy (removing one or both breasts)^[1].

Radiation therapy uses high-energy rays similar to X-rays to kill cancer cells. Radiation therapy following breast-conserving surgery decreases mortality and recurrence^[11]. It is commonly used after surgery to destroy any remaining cancer cells^[10].

Chemotherapy uses special medicines to shrink or kill cancer cells. The drugs can be pills you take or medicines given through your veins, or sometimes both^[10]. Chemotherapy circulates throughout the body in the bloodstream^[1].

Hormone therapy blocks cancer cells from getting the hormones they need to grow. Hormones like estrogen and progesterone can stimulate breast cancer cells to grow. Hormone therapy can block or lower the amount of these hormones in the body^[1][10].

Targeted therapy works by targeting specific differences in cancer cells that help them grow and survive. These drugs target specific molecules on cancer cells^[10][14].

Immunotherapy (also called biological therapy) works with the body’s immune system to help it fight cancer cells or to control side effects from other cancer treatments^[10].

The specific combination of treatments depends on factors such as the cancer’s stage, whether it has certain receptors, the HER2 status, whether the person has reached menopause, and overall health^[14]. Treatment options are tailored to be as effective as possible with the fewest possible side effects^[1].

Living with and after breast cancer

Living with breast cancer involves many emotional, physical, and practical challenges. It’s common to experience a range of emotions after a diagnosis of breast cancer. You may feel shocked, angry, anxious, sad, or depressed. You might wonder why breast cancer has happened to you. Some people feel quite alone or isolated^[24].

Treatment for breast cancer can cause physical changes to the body. If you’ve had breast cancer surgery, you may notice a change in your body size or shape. You might also have scars from surgery or the effects of treatment. Some types of treatment cause swelling. Hair loss from chemotherapy can range from mild thinning of hair to complete loss^[24].

Younger women with breast cancer may experience early menopause because of cancer treatment. Symptoms may include hot flushes, vaginal dryness, and loss of sexual desire. Some breast cancer treatments can also affect fertility^[24].

The weeks following a breast cancer diagnosis can be particularly stressful. You might find it hard to carry out normal everyday activities, to think clearly, eat, or sleep. It’s important to reach out for support. You can choose to share how you’re feeling with your treatment team, your partner and family members, or friends you trust^[24].

After treatment, you may have regular follow-up appointments to check how you are and see whether you have any problems or concerns^[12]. For many people, continuing to work during or after treatment can help provide a sense of normality^[18].

Today, there are more breast cancer survivors in the United States than any other group of cancer survivors. These days, breast cancer survivors often live long, satisfying, happy lives^[23]. Breast cancer survival rates have been increasing, and the number of people dying of breast cancer is steadily going down. Much of this is due to the widespread support for breast cancer awareness and funding for research. Advances in breast cancer screening allow healthcare professionals to diagnose breast cancer earlier, making it much more likely that the cancer can be cured^[2].

Reducing your risk

While you can’t change some risk factors such as family history, research shows that lifestyle changes can lower the chances of getting breast cancer, even in people at high risk^[17]. Some studies have shown that as many as 50 to 70% of breast cancers can be prevented depending on when people adopt risk-reducing behaviors and lifestyle changes^[22].

Ways to help reduce your breast cancer risk include^[17]:

• Limiting or avoiding alcohol: It’s safest not to drink alcohol. The more alcohol you have, the greater your risk of getting breast cancer. In general, women should have no more than one drink a day
• Maintaining a healthy weight: If your weight is healthy, work to maintain it. If you need to lose weight, ask your healthcare professional how to do so
• Getting physically active: Physical activity can help you stay at a healthy weight. Try to move more and sit less. Most healthy adults should aim for regular exercise
• Not smoking: Smoking increases the risk of many cancers and other health conditions

A healthy lifestyle includes maintaining a healthy weight, eating a healthy diet, limiting alcohol, getting physical activity, and not smoking. These healthy behaviors are linked to a lower risk of breast cancer recurrence and improved survival^[21].