Breast Neoplasm

Breast neoplasm, commonly known as breast cancer, is a disease where cells in the breast tissue grow out of control and form tumors. While it most often affects women over 50, it can also occur in younger women and men. With advances in early detection and treatment, many people diagnosed with breast cancer can be successfully treated and go on to live long, healthy lives.

Table of contents

• What is breast cancer?
• How the breast is structured
• Types of breast cancer
• Signs and symptoms
• Who is at risk?
• How breast cancer is diagnosed
• Treatment options
• How common is breast cancer?

What is breast cancer?

Breast cancer is a disease in which cells in the breast grow out of control and form tumors^[1]. When breast cells change and no longer grow or behave normally, they can become cancerous. If left untreated, these tumors can spread throughout the body and become life-threatening^[4].

Breast cancer is one of the most common cancers affecting women. About 80% of breast cancer cases are invasive, meaning a tumor may spread from the breast to other areas of the body^[1]. However, breast cancer is not only a women’s disease. Although approximately 99% of breast cancers occur in women, about 0.5 to 1% of cases occur in men^[4].

The condition typically affects women age 50 and older, but it can also affect women who are younger than 50^[1]. In the United States, an estimated 316,950 new cases of invasive breast cancer are expected in 2025, along with about 59,080 cases of a precancerous condition^[9].

How the breast is structured

Each breast is made up of three main parts: lobules, ducts, and connective tissue^[2]. The lobules are small glands that produce milk. The ducts are thin tubes that carry milk from the lobules to the nipple. The connective tissue, which consists of fibrous and fatty tissue, surrounds and holds everything together.

Each breast has 15 to 20 sections called lobes, and each lobe contains many smaller sections called lobules^[9]. Lobules end in dozens of tiny bulbs that can make milk. These structures are all linked by thin tubes called ducts. The breast also contains blood vessels and lymph vessels, which carry a nearly colorless fluid called lymph. Lymph vessels connect to small, bean-shaped structures called lymph nodes, which filter lymph and store white blood cells that help fight infection and disease^[9].

Types of breast cancer

Breast cancer can begin in different parts of the breast, and healthcare providers classify cancers based on where they start and how they behave. The most common types include:

Invasive ductal carcinoma (IDC) is the most common type of breast cancer in the United States. This cancer starts in the milk ducts and spreads to nearby breast tissue. About 70% to 80% of all breast cancers are invasive ductal carcinoma^[1][2]. Cancer cells can also spread through the lymph nodes or bloodstream to other parts of the body^[2].

Invasive lobular carcinoma (ILC) is the second most common type of breast cancer. This cancer starts in the lobules, the milk-producing glands, and spreads to nearby breast tissues. About 10% to 15% of breast cancers are invasive lobular carcinoma^[1][2]. Unlike invasive ductal carcinoma, which typically forms a lump, invasive lobular carcinoma appears as thickened connective tissue in the breast, making it harder to see on a mammogram^[2].

Ductal carcinoma in situ (DCIS) is a condition where cancer cells are found only in the lining of the milk ducts and have not spread to other tissues in the breast. Like invasive ductal carcinoma, this cancer starts in the milk ducts, but the difference is that DCIS doesn’t spread beyond the ducts^[1]. This is considered a precancerous or early-stage condition.

Less common types of breast cancer include:

• Triple-negative breast cancer (TNBC): This invasive cancer is aggressive and spreads more quickly than other breast cancers^[1].
• Inflammatory breast cancer (IBC): This rare, fast-growing cancer looks like a rash on the breast. It is rare in the United States^[1]. In inflammatory breast cancer, cancer cells block the lymph vessels in the skin of the breast, making it feel warm and look red and swollen^[2].
• Paget’s disease of the breast: This rare cancer affects the skin of the nipple and may look like a rash. Less than 4% of all breast cancers are Paget’s disease of the breast^[1].

Healthcare providers also classify breast cancer by receptor cell status. Receptors are protein molecules on cells’ surfaces that can attract or attach to certain substances in the blood, including hormones like estrogen and progesterone. These hormones help cancerous cells to grow^[1]. Finding out if cancerous cells have these receptors helps healthcare providers plan treatment.

Breast cancer subtypes include:

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

Signs and symptoms

Breast cancer can affect the breasts in different ways. Some symptoms are very distinctive, while others may simply appear as areas that look very different from the rest of the breast. Some people do not have any signs or symptoms at all^[2].

Warning signs of breast cancer may include^[1][6]:

• A new lump in the breast or underarm (armpit)
• Thickening or swelling of part of the breast
• 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
• Irritation or dimpling of breast skin
• Redness or flaky skin in the nipple area or the breast
• A change in the look or feel of the skin on the breast or nipple (skin may look dimpled, puckered, scaly, or inflamed; it may look red, purple, or darker than other parts of the breast)
• Pulling in of the nipple or pain in the nipple area
• Nipple discharge other than breast milk, including blood
• Any change in the size or shape of the breast
• Pain in any area of the breast

It’s important to remember that these symptoms can happen with other conditions that are not cancer^[1]. Many conditions can cause lumps in the breast, and most breast lumps are caused by other medical conditions^[6]. If you have any signs or symptoms that worry you, be sure to see your doctor right away.

Who is at risk?

Studies have shown that risk for breast cancer is due to a combination of factors. The main factors that influence risk include being a woman and getting older. Most breast cancers are found in women who are 50 years old or older^[6]. Roughly half of all breast cancers occur in women with no specific risk factors other than sex and age^[4].

Risk factors for breast cancer include^[6]:

• Genetic mutations: Women who have inherited changes (mutations) to certain genes, such as BRCA1 and BRCA2, are at higher risk of breast and ovarian cancer
• Reproductive history: Starting menstrual periods before age 12 and starting menopause after age 55 expose women to hormones longer, raising their risk of getting breast cancer
• Having dense breasts: Dense breasts have more connective tissue than fatty tissue, which can make it harder to see tumors on a mammogram
• Family history: Having a close blood relative with breast cancer increases risk
• Personal history of breast cancer: Women who have had breast cancer are more likely to get breast cancer a second time
• Personal history of certain breast conditions: Women who have had certain non-cancerous breast diseases are at increased risk
• Radiation therapy to the chest: Women who had radiation therapy to the chest or breasts before age 30 have a higher risk
• Hormone therapy: Taking combination estrogen plus progestin hormone replacement therapy increases risk
• Alcohol intake: Drinking alcoholic beverages is linked to increased breast cancer risk
• Obesity (after menopause): Being overweight or obese after menopause raises the risk
• Nulliparity or older age at first birth: Women who have never had children or who had their first child after age 30 have a slightly higher breast cancer risk

Having a risk factor does not mean you will get the disease, and not all risk factors have the same effect. Most women have some risk factors, but most women do not get breast cancer^[6]. If you have breast cancer risk factors, talk with your doctor about ways you can lower your risk and about screening for breast cancer.

How breast cancer is diagnosed

Breast cancer diagnosis often begins with an exam and a discussion of symptoms. Tests that examine the breasts are used to diagnose breast cancer^[9][10].

Clinical breast exam: During this exam, a healthcare professional looks at the breasts for anything that’s not typical, such as changes in the skin or nipple. Then the health professional feels the breasts for lumps and also feels along the collarbones and around the armpits for lumps^[10].

Mammogram: A mammogram is an X-ray of the breast tissue. Mammograms are commonly used to screen for breast cancer. If a screening mammogram finds something concerning, additional tests may be needed^[10].

Breast ultrasound: This test uses sound waves to create images of breast tissue. It can help determine whether a breast lump is solid or filled with fluid^[10].

Breast MRI (Magnetic Resonance Imaging): This test uses magnets and radio waves to create detailed images of the inside of the breast^[10].

Biopsy: To confirm whether there is cancer or not, a sample of tissue is removed from the breast for testing. The sample is sent to a lab where doctors called pathologists examine it^[10]. A biopsy is the only way to definitively diagnose breast cancer.

After a diagnosis of breast cancer, all tissue samples are tested to identify whether the cancer cells have estrogen, progesterone, or HER2 receptors. This information helps guide treatment decisions^[14].

Treatment options

Treatment for breast cancer depends on several factors, including where the cancer is, how big it is, the type of breast cancer, whether the cancer cells have certain proteins (receptors), and your general health^[16]. People with breast cancer often get more than one kind of treatment^[12].

The main treatments for breast cancer include^[12]:

Surgery: This is an operation in which doctors cut out the cancer. Surgery is often the first treatment for breast cancer^[16]. There are two main surgical options with similar survival rates. A lumpectomy removes the tumor and a small amount of surrounding tissue, and is typically followed by radiation therapy if the tumor can be removed completely with good cosmetic results. A mastectomy removes all breast tissue from one or both breasts^[14].

Chemotherapy: This treatment uses special medicines to shrink or kill the cancer. The drugs can be pills you take or medicines given through your veins, or sometimes both^[12]. Chemotherapy uses anti-cancer (also called cytotoxic) drugs to destroy cancer cells, and the drugs circulate throughout the body in the bloodstream^[11].

Radiation therapy: This treatment uses high-energy rays (similar to X-rays) to kill cancer cells^[12]. Radiation therapy is a common treatment for breast cancer and uses high-energy X-rays to destroy cancer cells^[16].

Hormone therapy: This treatment blocks cancer cells from getting the hormones they need to grow^[12]. Hormones can stimulate breast cancer cells to grow, so hormone therapy can block or lower the amount of hormones in the body. One of the most common types is a medication called tamoxifen^[11].

Targeted therapy: Targeted cancer drugs work by targeting the differences in cancer cells that help them to grow and survive^[16].

Immunotherapy: This treatment works with your body’s immune system to help it fight cancer cells or to control side effects from other cancer treatments^[12]. Immunotherapy uses the immune system to fight cancer^[16].

Treatment typically has three phases for early and locally advanced breast cancer. The preoperative phase may use systemic therapies such as endocrine therapy or immunotherapy when tumors express certain receptors. Chemotherapy may also be used before surgery^[14]. The surgical phase involves either lumpectomy with radiation or mastectomy, along with evaluation of lymph nodes when there is suspected disease^[14]. The postoperative phase may include radiation, endocrine therapy, immunotherapy, and chemotherapy^[14].

For stage IV (metastatic) breast cancer, where the cancer has spread to other parts of the body, treatment is focused on improving the length and quality of life. While metastatic breast cancer is treatable, it is not currently curable^[14].

How common is breast cancer?

Breast cancer is one of the most common cancers affecting women worldwide. 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^[4].

In the United States, an estimated 316,950 women will be diagnosed with invasive breast cancer in 2025. About 42,170 women diagnosed with breast cancer—fewer than one in eight—will die of the disease^[9]. Breast cancer is the most common cancer diagnosed in women, accounting for more than 1 in 10 new cancer diagnoses annually^[5].

Breast cancer was the most common cancer in women in 157 countries out of 185 in 2022^[4]. 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].

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 widespread support for breast cancer awareness and funding for research. Advances in breast cancer screening allow healthcare professionals to diagnose breast cancer earlier, and finding the cancer earlier makes it much more likely that the cancer can be cured^[3].