How does breast cancer start?

Symptoms of breast cancer include a lump in the breast, bloody discharge from the nipple, and changes in the shape or texture of the nipple or breast. Doctors know that breast cancer occurs when certain breast cells begin to grow abnormally. These cells divide more quickly than healthy cells and continue to build up, forming a lump or mass. The cells can spread (metastasize) through the breast to the lymph nodes or to other parts of the body.

Breast cancer is a type of cancer that starts in the breast. It may start in one or both breasts. Breast cancer begins when breast cells (such as those that line the ducts and lobes) begin to grow abnormally. These cells have the potential to grow out of control and invade surrounding tissue.

When this happens, it's called invasive breast cancer. If cancer cells continue to grow, they can spread beyond the breast to other parts of the body, potentially life-threatening. Breast cancer occurs when there are changes in genetic material (DNA). The exact cause of these genetic changes is often unknown.

The most common breast cancers, such as ductal carcinoma in situ (DCIS) and invasive carcinoma, are adenocarcinomas, since the cancers originate in cells of the glands in the milk ducts or in the lobules (milk-producing glands). Some women have bothersome signs and symptoms during menopause, and for these women, the increased risk of breast cancer may be acceptable to alleviate the signs and symptoms of menopause. In this case, it attacks breast tissue cells and there is not a single thing that causes these DNA mutations. Although a lump in the breast is a common symptom of breast cancer, not all breast cancers have obvious symptoms.

Breast cancer can spread when cancer cells enter the blood or lymphatic system and are then transported to other parts of the body. Connect with others like you for support and answers to your questions in the Mayo Clinic Connect breast cancer support group, a community of patients. There are several other less common types of breast cancer, such as Paget's disease and medullary, mucinous and inflammatory breast cancer. However, it's important to see your doctor if you notice new lumps or other unusual changes in your breasts as soon as possible.

If you have a significant family history of breast cancer or other types of cancer, your doctor may recommend a blood test to help identify specific BRCA mutations or other genes that are transmitted from parent to child. Staging involves testing to determine if the cancer has spread within the breast or to other parts of the body. Any lump or change in the breast should be examined by a health professional to determine if it is benign or malignant (cancer) and if it could affect your future risk of cancer. Mammograms used to evaluate an abnormal breast symptom (such as a lump in the breast or a suspicious mass on a screening mammogram) are called diagnostic mammograms.

If the disease has spread beyond the breasts and lymph nodes, surgery is usually not recommended and the main treatment is medical therapy. If the cancer is found in the lymph nodes, there is a greater chance that the cells have traveled through the lymphatic system and blood stream to spread (metastasize) to other parts of the body.

Tonya Sharrai
Tonya Sharrai

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