Understanding How Common Breast Cancer Is

Breast cancer stands as one of the most frequently diagnosed cancers in women around the world. In 2022 alone, approximately 2.3 million women received a breast cancer diagnosis globally, with an estimated 670,000 deaths occurring that same year^[4]. This cancer occurs in every country across the globe, affecting women at any age after puberty, though rates tend to increase as women grow older^[4].

The statistics reveal striking differences based on where people live and the resources available to them. In countries with very high human development, about one in 12 women will be diagnosed with breast cancer during their lifetime, while one in 71 will die from it. The picture looks different in countries with lower development levels: although only one in 27 women receives a breast cancer diagnosis, one in 48 will die from the disease^[4]. This shows that while fewer women may be diagnosed in less developed regions, the disease often proves more deadly there.

After skin cancer, breast cancer is the most common cancer diagnosed in women in the United States. In fact, it accounts for more than one in 10 new cancer diagnoses each year^[5]. Breast cancer was the most common cancer in women across 157 out of 185 countries in 2022^[4].

While breast cancer primarily affects women, men can develop it too. About 99% of breast cancer cases occur in women, while approximately 0.5 to 1% occur in men^[4]. The condition typically affects women aged 50 and older, but it can also strike younger women^[1]. Today, there are approximately four million breast cancer survivors in the United States, more than any other group of cancer survivors^[23].

What Causes Breast Cancer to Develop

Breast cancer develops when cells in the breast tissue undergo changes that cause them to grow and multiply abnormally. These cells can form tumors, which are masses of tissue that may be felt as lumps or seen on imaging tests. The disease most commonly starts in the ductal epithelium, which is the lining of the milk ducts that carry milk from the glands to the nipple. This type is called ductal carcinoma. Breast cancer can also begin in the lobules, the groups of glands that produce milk, resulting in lobular carcinoma^[5].

The earliest form of breast cancer, known as in situ cancer, remains where it started and has not yet spread into surrounding breast tissue. If left unchecked, cancer cells can invade nearby breast tissue, a process called invasion. Once this happens, the tumors can spread to nearby lymph nodes, which are small bean-shaped structures that filter fluid and help fight infection, or to other organs in the body. When cancer spreads to distant parts of the body, it is called metastasis, and this stage can become life-threatening^[4].

The breasts are made up of lobes and ducts. Each breast contains 15 to 20 sections called lobes, and each lobe has many smaller sections called lobules. These lobules end in dozens of tiny bulbs that can produce milk. The lobes, lobules, and bulbs are connected by thin tubes called ducts. The breasts also contain blood vessels and lymph vessels, which carry lymph fluid throughout the body^[9].

Some breast cancers are caused by inherited changes in genes. These are mutations passed down from parents to children. Certain genetic abnormalities can significantly increase a person’s risk of developing breast cancer during their lifetime^[2]. However, many cases of breast cancer occur in women with no specific risk factors other than being female and growing older^[4].

Who Is at Higher Risk of Developing Breast Cancer

Being female is the strongest risk factor for breast cancer. While men can develop the disease, the overwhelming majority of cases occur in women^[4]. Age also plays a significant role, as the risk of breast cancer continues to increase as women get older^[5].

A family history of breast cancer can increase risk, especially if close relatives such as a mother, sister, or daughter have been diagnosed with the disease. Inherited genetic mutations, particularly in genes called BRCA1 and BRCA2, can dramatically increase a woman’s likelihood of developing breast cancer^[9]. However, having a family history does not guarantee that someone will develop breast cancer, and many women with breast cancer have no family history of the disease^[4].

Other factors that can increase breast cancer risk include starting menstruation at an early age, going through menopause at a later age, having the first child at an older age, never having children, and not breastfeeding. Each of these factors affects how long breast tissue is exposed to hormones like estrogen and progesterone, which can influence cancer development^[5].

Lifestyle factors also contribute to breast cancer risk. Drinking alcohol increases risk, and the more alcohol consumed, the greater the risk becomes. Even small amounts can raise the likelihood of developing breast cancer^[17]. Being overweight or obese, particularly after menopause, is linked to increased breast cancer risk. Physical inactivity and not exercising regularly can also contribute to higher risk^[5].

Using hormone replacement therapy, particularly therapies that combine estrogen and progesterone, can increase breast cancer risk. The longer these therapies are used, the higher the risk becomes. Oral contraceptives may also slightly increase risk while they are being used^[5].

Recognizing the Signs and Symptoms

Breast cancer can affect the breasts in many different ways, and sometimes it causes no noticeable symptoms at all. When symptoms do appear, they can vary widely from person to person. One of the most common signs is a lump or mass in the breast, which may feel as small as a pea. Some lumps or areas of thickening in or near the breast or in the underarm area may persist through the menstrual cycle^[1].

Changes in the size, shape, or contour of the breast can signal a problem. The skin on the breast or nipple may change in appearance or texture, sometimes looking dimpled, puckered, scaly, or inflamed. The skin might appear red, purple, or darker than other parts of the breast^[1]. These changes occur because cancer cells can affect the skin and underlying tissues in ways that alter the breast’s appearance.

Nipple changes are another important warning sign. The nipple may turn inward, a condition called nipple retraction. Some people notice discharge from the nipple that is not breast milk, which can be clear, bloody, or another color. Pain in the nipple area, while not always a sign of cancer, should be evaluated by a healthcare provider^[2].

It is important to understand that many breast changes are not cancerous. Benign conditions such as cysts, infections, or hormonal fluctuations can cause lumps or other symptoms. However, any persistent change in the breast should be examined by a healthcare professional to determine its cause^[1].

Steps to Help Prevent Breast Cancer

While some risk factors for breast cancer cannot be changed, such as age and genetics, there are lifestyle choices that can help lower risk. Research shows that making healthy changes can reduce the chances of developing breast cancer, even in people at higher risk^[17].

Limiting or avoiding alcohol is one important step. The safest approach is not to drink alcohol at all, but for those who choose to drink, moderation is key. Women should limit themselves to no more than one drink per day, as even small amounts of alcohol can increase breast cancer risk. One drink is roughly equivalent to 12 ounces of beer, 5 ounces of wine, or 1.5 ounces of distilled spirits^[17].

Maintaining a healthy weight is crucial for breast cancer prevention. Being overweight or obese, especially after menopause, increases the risk of developing breast cancer. People who need to lose weight should work with their healthcare provider to develop a safe and effective plan. Eating fewer calories, watching portion sizes, and gradually increasing physical activity can all help achieve and maintain a healthy weight^[17].

Regular physical activity helps keep weight in check and provides many other health benefits. Most healthy adults should aim for at least 150 minutes of moderate aerobic activity or 75 minutes of vigorous activity each week. Physical activity can include brisk walking, jogging, swimming, cycling, or any other form of exercise that gets the body moving^[17].

Breastfeeding, when possible, may help reduce breast cancer risk. The longer a woman breastfeeds, the greater the protective effect may be. Not smoking and avoiding exposure to secondhand smoke also contribute to overall cancer prevention^[22].

For women at high risk due to family history or genetic mutations, there may be additional preventive options to discuss with healthcare providers. These might include more frequent screening, preventive medications, or in some cases, preventive surgery. However, these decisions are highly individual and should be made in consultation with medical professionals who understand the specific circumstances^[17].

How Breast Cancer Changes the Body

When breast cancer develops, it causes changes at the cellular and tissue level that affect how the body normally functions. Cancer begins when normal breast cells undergo genetic changes that cause them to grow out of control. Unlike healthy cells, which grow, divide, and die in an orderly way, cancer cells continue to multiply without stopping and can live much longer than normal cells^[4].

As these abnormal cells accumulate, they form tumors. Tumors are masses of tissue that can be felt as lumps during a physical examination or seen on imaging tests. Not all tumors are cancerous; some are benign, meaning they do not invade surrounding tissues or spread to other parts of the body. However, malignant tumors, which are cancerous, can grow into nearby tissues and spread through the blood or lymphatic system to distant organs^[4].

The lymphatic system plays an important role in how breast cancer spreads. Lymph vessels carry lymph fluid, which contains white blood cells that help fight infection. When cancer cells enter lymph vessels, they can travel to nearby lymph nodes under the arm, above the collarbone, or in the chest. Once cancer reaches lymph nodes, it has the potential to spread to other parts of the body, including the bones, liver, lungs, or brain^[9].

Different types of breast cancer affect the body in different ways. The most common type, invasive ductal carcinoma, starts in the milk ducts and spreads to nearby breast tissue. Invasive lobular carcinoma begins in the milk-producing lobules and can also spread. Some rare forms, such as inflammatory breast cancer, cause the cancer cells to block lymph vessels in the skin of the breast, leading to redness, swelling, and a skin texture that resembles an orange peel^[1].

Cancer cells can have different characteristics that influence how they grow and respond to treatment. Some breast cancer cells have receptors, which are protein molecules on the cell surface that can attach to hormones like estrogen and progesterone. When these hormones attach to receptors, they can stimulate cancer cells to grow. Other cancer cells produce high levels of a protein called HER2, which also promotes cell growth. Understanding these characteristics helps doctors choose the most effective treatments^[1].

Treatment for breast cancer can also cause changes in the body. Surgery to remove tumors or breast tissue can alter the size and shape of the breast. Chemotherapy and radiation therapy work by killing cancer cells, but they can also affect healthy cells, leading to side effects such as fatigue, hair loss, and changes in blood counts. Hormone therapies that block estrogen or progesterone can cause symptoms similar to menopause, including hot flashes and vaginal dryness^[23].

After treatment, the body’s immune system and other healing processes work to repair damage and restore normal function. Some changes may be temporary, while others can be permanent. Understanding how breast cancer and its treatments affect the body helps patients and their families prepare for the journey ahead and work with healthcare teams to manage symptoms and maintain quality of life^[4].