What Is Breast Cancer? Symptoms and Causes

Breast cancer develops when cells in the breast tissue begin to grow and multiply uncontrollably. It is the most common cancer in women, and although it is rare, it can also occur in men. Because the disease often causes no symptoms in its early stages, regular check-ups should not be skipped. A newly noticed lump, a change in the shape of the breast, a change in skin color or a change in the nipple can be among the first signs of breast cancer. For this reason, it is important to keep track of any changes in your breasts and to see a doctor without delay if you notice anything unusual.

What Is Breast Cancer?

Breast cancer is a type of cancer that arises when cells in the breast tissue divide and multiply uncontrollably for a variety of reasons. The breast is made up of milk-producing lobules (glands), the ducts that carry milk to the nipple, and the fatty and connective tissue that surrounds these structures. Most breast cancers start in the cells lining the milk ducts, but the disease can also begin in the lobules or in other tissues of the breast.
Cells are living structures with a defined life cycle. Under normal conditions, cells that age or become seriously damaged are removed in a controlled way and replaced by new ones. When the mechanisms that regulate cell growth and division break down, however, cells may keep dividing even when the body does not need them, and over time this can lead to the formation of a tumor. According to 2024 data from the World Health Organization, breast cancer is the second most common cancer in the general population after lung cancer, and the most common cancer in women.

What Are the Types of Breast Cancer?

Breast cancer is broadly divided into two groups, invasive and non-invasive, depending on whether the cancer cells have spread beyond the area where they started. In non-invasive breast cancer, the cells remain confined to their site of origin, whereas in invasive types they begin to spread into the surrounding breast tissue. The main types of breast cancer are:

• Ductal carcinoma in situ (DCIS): A non-invasive breast cancer that starts in the milk ducts, with the cancer cells remaining confined within the duct.
• Invasive ductal carcinoma (IDC): An invasive breast cancer that starts in a milk duct, then breaks through the duct wall and spreads into the surrounding breast tissue. It is the most common type of breast cancer.
• Invasive lobular carcinoma (ILC): An invasive breast cancer that starts in the milk-producing glands and later spreads into the surrounding breast tissue. It is the second most common type after IDC.
• Inflammatory breast cancer: A rare but potentially fast-growing form of breast cancer. Studies show that it accounts for approximately 1–5% of all breast cancer cases. It develops when cancer cells block the lymphatic vessels in the skin of the breast. Early signs of inflammatory breast cancer may include swelling and a change in the color of the breast.
• Paget disease of the nipple: A rare breast cancer that occurs when cancer cells originating in the milk ducts spread to the nipple and the surrounding areola. It may present with changes such as redness, scaling and crusting of the nipple.
• Angiosarcoma: A rare cancer that develops from the cells lining the blood or lymph vessels in the breast tissue.

Although it is sometimes listed among the types of breast cancer, lobular carcinoma in situ (LCIS) is not breast cancer. It refers to abnormal changes in the cells of the milk-producing glands; these cells do not spread outside the lobules into the surrounding breast tissue. It is not yet clear whether LCIS is a precancerous condition or a risk factor for developing breast cancer. Even so, people with LCIS may have a higher risk of developing breast cancer later in life.

What Are the 12 Symptoms of Breast Cancer?

Breast cancer may not cause any symptoms in its early stages. Most people are diagnosed after noticing a lump in the breast, while in some patients a rash may be an early sign. With this in mind, the main symptoms of breast cancer are as follows:

 A new lump in the breast that was not there before is one of the most common symptoms of breast cancer. However, not every breast lump is caused by cancer. Conditions such as fibrocystic breasts or breast cysts are different from cancer. Lumps caused by breast cancer are usually painless, whereas fibrocystic breasts and breast cysts can sometimes be painful, particularly before a menstrual period. Cancerous lumps also tend to have an irregular shape. That said, some may be painful or round. For this reason, any lump in the breast should first be evaluated for cancer.

• Thickening of the breast skin may occur, especially in invasive lobular carcinoma, the type that originates in the milk-producing glands.
• It is normal for one breast to be a slightly different size from the other. In breast cancer, however, a noticeable change in the size of one breast may appear where there was none before. Any unexplained swelling or enlargement that develops over a short period should therefore be assessed by a specialist.
• A new change in the outline or shape of the breast may be noticed. Changes in the breast tissue can make one part of the breast look different from the rest.
• Redness, discoloration or an irritated appearance may develop on the skin of the breast. These changes are seen more often in certain rare types, such as inflammatory breast cancer.
• Dimpling or puckering of the breast skin may occur.
• The pores of the breast skin may become more prominent, giving it an orange-peel appearance, particularly in inflammatory breast cancer.
• A nipple that turns inward (inverted nipple) or becomes flattened may be a sign of breast cancer.
• Scaling, crusting or sores on the nipple: Redness, scaling or crusting may be seen on the nipple and the surrounding areola.
• Nipple discharge in women who are not breastfeeding can have other causes, such as hormonal imbalances, but any discharge occurring outside the breastfeeding period should be investigated for cancer.
• When breast cancer spreads to the lymph nodes in the armpit, a lump or swelling may be felt there.
• Breast cancer usually does not cause pain. Breast pain is more likely to be due to hormonal changes, cysts or other benign causes. Nevertheless, pain that does not go away, gets worse over time or occurs together with swelling or skin changes in the breast should be evaluated by a specialist.

Breast cancer symptoms can vary depending on the stage of the disease. Although pain is often thought of as a sign of breast cancer, the lumps are actually painless in most cases. In addition, having a lump in the breast does not always mean cancer. This is why breast cancer is frequently detected during a routine examination.

What Are the Symptoms of Breast Cancer in Men?

Although breast cancer is the most common cancer in women, it can also occur in men, albeit rarely. Breast cancer symptoms in men are largely the same as those seen in women. A lump in the breast or around the nipple, an inverted nipple, redness, scaling or dimpling of the breast skin, and nipple discharge are among the symptoms that can also occur in men.
Because men have less breast tissue than women, tumors usually develop beneath or around the nipple. The most common sign in men is therefore a firm, usually painless lump near the nipple. Swelling in the armpit or around the collarbone may also be a sign of breast cancer.

What Causes Breast Cancer?

Breast cancer develops when changes in the genetic makeup of cells in the breast tissue cause them to multiply uncontrollably. Although it is not fully understood why these changes occur, certain factors are known to increase the risk. These include non-modifiable factors such as age, genetic predisposition and dense breast tissue, as well as modifiable factors such as lifestyle habits. The main causes and risk factors of breast cancer are discussed below:

• Age is one of the most important known risk factors for breast cancer, mainly because the majority of cases are diagnosed at an average age of around 62. This does not mean, however, that breast cancer only affects older women. Research shows that the incidence of breast cancer in women under 50 is rising by about 1.4% each year. As a result, there is no simple answer to the question “At what age does breast cancer occur?” Since routine screening programs generally cover women aged 40 and over, breast cancer symptoms in young women are usually first noticed during breast self-examination.
• An inherited gene mutation passed down from a parent plays a role in approximately 5–10% of breast cancer cases. Research suggests that mutations in the BRCA1 and BRCA2 genes in particular can raise a woman's risk of developing breast cancer to around 60%.
• A family history of breast cancer does not necessarily mean that a person carries the same mutated gene, but having a first-degree relative with breast cancer can increase the risk.
• Women who start menstruating early (before age 12) or reach menopause late (after age 55) may have a higher risk of estrogen receptor (ER)-positive breast cancer.

The factors listed above are non-modifiable risk factors for breast cancer. There are also modifiable risk factors, including smoking, alcohol use, obesity and exposure to endocrine-disrupting substances such as BPA, arsenic and lead. A diet high in refined foods and in fatty and sugary products may also increase the risk of several cancers, including breast cancer.

How Is Breast Cancer Diagnosed?

Diagnosis begins with a review of the patient's complaints and medical history, followed by a physical examination of the breasts and armpits. The doctor checks for any palpable lump, change in shape, skin changes or changes in the nipple. If needed, specialists may order imaging tests to examine the breasts in more detail.
Mammography and breast ultrasound are the imaging methods most commonly used in the diagnosis and screening of breast cancer. The digital mammography used at Yeditepe University Hospitals can provide detailed images of the breast tissue with a low dose of radiation. Ultrasound, in turn, allows a closer look at any atypical area seen on a mammogram. If there is a lump or other change that could be an early sign of breast cancer, the doctor may use both methods. In addition, when breast cancer symptoms in breastfeeding mothers are present, ultrasound may be preferred over mammography.
Since not every breast lump is cancerous, a biopsy may be needed if imaging reveals a suspicious area. During a biopsy, a tissue sample is taken from the suspicious area and examined in a pathology laboratory. If cancer is confirmed, specialists may order additional tests to determine the type of cancer.

What Are the Stages of Breast Cancer?

Once breast cancer has been diagnosed, staging is needed to determine how far the disease has progressed and to plan treatment. Staging takes into account the size and location of the tumor in the breast, whether cancer cells have spread to nearby lymph nodes and whether they have spread to other parts of the body.
Breast cancer is staged using the TNM system. “T” describes the size and extent of the tumor, “N” indicates whether it has spread to nearby lymph nodes, and “M” indicates whether the cancer has metastasized to distant sites. The characteristics of the cancer cells may also be taken into account. How the cells look under the microscope, whether they have hormone receptors and whether they overproduce a protein called HER2 all help define the disease and guide the treatment approach. On this basis, the stages of breast cancer are as follows:

• Stage 0 breast cancer: The cancer cells are found in the milk ducts and have not spread to other areas. Stage 0 is used to describe the non-invasive breast cancer known as ductal carcinoma in situ.
• Stage 1 breast cancer: The cancer has spread into the breast tissue and become invasive. In stage 1A, the tumor is generally 2 cm or smaller and has not spread to nearby lymph nodes. In stage 1B, there may be no visible tumor in the breast, or the tumor may be 2 cm or smaller, but small clusters of cancer cells are found in nearby lymph nodes.
• Stage 2: The tumor may be larger or may have spread to nearby lymph nodes. In stage 2A, the tumor is smaller than 2 cm and may have spread to up to three lymph nodes, or it measures 2–5 cm and has not spread to the lymph nodes. In stage 2B, the tumor measures 2–5 cm and has spread to nearby lymph nodes, or it is larger than 5 cm but has not spread to the lymph nodes.
• Stage 3: In addition to the breast tissue, the cancer may have spread to the chest wall, the skin of the breast or a larger number of lymph nodes. Stage 3A refers to cases in which four to nine lymph nodes are involved or, in some cases, a larger tumor has spread to up to three lymph nodes. In stage 3B, the cancer may have spread to the chest wall or the skin of the breast. In stage 3C, there is more extensive spread to the lymph nodes in the armpit, around the collarbone or near the breastbone.
• Stage 4: The cancer has spread beyond the breast and nearby lymph nodes to distant organs such as the bones, lungs, liver or brain. This stage is also known as metastatic breast cancer. Symptoms of metastatic breast cancer depend on the organ to which the cancer has spread. For example, spread to the bones may cause bone pain, and spread to the lungs may cause shortness of breath.

The stage of breast cancer provides important information for treatment planning. When preparing a treatment plan, however, specialists also consider the features of the tumor, whether the cancer cells use hormones such as estrogen and progesterone to grow (in other words, whether the cancer is hormone receptor-positive) and the patient's overall health. Because symptoms of advanced breast cancer can include severe pain, the patient's symptoms are taken into account alongside the stage when planning treatment.

How Is Breast Cancer Treated?

Treatment is planned according to the stage of the disease, the size and characteristics of the tumor, the patient's age at diagnosis and their overall health. Surgery and non-surgical options such as chemotherapy may be used alone or in combination. Surgery is one of the most common treatments for breast cancer. Depending on the case, the surgeon may perform breast-conserving surgery, which removes the entire tumor along with a margin of surrounding tissue, or, when necessary, remove the whole breast (mastectomy). A sentinel lymph node biopsy may be performed during surgery to find out whether the cancer has spread to the lymph nodes. If cancer cells are found in the lymph nodes, more extensive lymph node surgery may be required.
Radiation therapy may be given, particularly after breast-conserving surgery and in some patients after mastectomy. It uses high-energy rays to destroy cancer cells or reduce the risk of the cancer coming back.
Chemotherapy is one of the most widely used treatments for cancer, including breast cancer. It uses drugs to destroy cancer cells and can be given before surgery to shrink the tumor or after surgery to eliminate any cancer cells that may remain. Not every cancer patient needs chemotherapy, however. In suitable patients, specialists may also use chemotherapy-free cancer treatment options such as immunotherapy, smart drugs and next-generation targeted therapies.
If the cancer is hormone-sensitive, hormone therapy may be used. By blocking the production of hormones such as estrogen and progesterone that can fuel the growth of breast cancer, hormone therapy can help stop the cancer from growing or eliminate it altogether.
Follow-up continues after treatment. Regular check-ups are used to monitor whether the disease has returned and whether any new changes have appeared. If you notice anything that could be a sign of breast cancer recurrence, it is important to consult your doctor without delay.
Because breast cancer often progresses without symptoms, it is frequently detected only through routine screening. Early diagnosis has a major impact on the success of treatment. If you notice a lump in your breast, a skin change or a change in your nipple, or if you simply want to be screened, you can have the necessary check-ups with the specialist doctors at Yeditepe University Hospitals.