Understanding Breast Cancer

The earlier a breast cancer lump is found, identified, and treated, the better the outlook. That’s why breast cancer testing plays such a key role in so many facets of the disease.

Unfortunately, signs of breast cancer are rarely visible from the surface of the skin. Breast self-exams should be done regularly to detect physically substantial lumps under the skin. But even self-exams may miss some cases. By moving the slide from left to right, you will see where (in most cases) breast cancer develops: deep down in the inner structures of the breast, within the ducts. 

Cancer begins deep down in the body, at the cellular level. Cells are the basic building blocks of the human body, and are constantly growing and dividing in a controlled manner to create new tissues. Normally, new cells replace older cells as they die out. However, cells can mutate for a variety of factors—including chemicals, heredity, and others—leading to unchecked cell growth.

The breast ducts are lined with epithelial cells, a cell type that, when mutated, replicates easily and freely because they lose adhesion to other cells. Cancer that begins in the ducts is called ductal carcinoma—this is the most common type of breast cancer.

Tumors form when the cell regrowth process gets mixed up and cells do not die when they should. These damaged cells continue to mutate and grow uncontrollably. The cause of this is still largely unknown. As cancerous epithelial cells begin to reproduce and take up space in the breast ducts, the pressure can force a liquid discharge from the nipple. Not all nipple discharge indicates cancer, but it is a good reason to see your doctor.

Your doctor will use a number of diagnostic methods, potentially including x-rays (mammography) and breast MRIs to determine whether you do in fact have a cancerous growth.

A mammogram is a breast X-ray, and is used to screen for breast cancer in women who have no signs of the disease, or to further diagnose a woman who has discovered a lump. Although there is some debate, a mammography is typically recommended every year or two for women over 40 (or 50).

The image here is a split screen: on the left is a mammogram showing a cancerous lump in the breast duct; on the right is an illustration showing the same cancer-stricken breast. If you move the slider from left to right, the illustration will help you understand the X-ray image that your doctor sees in his or her office. 

Magnetic resonance imaging (MRI) uses radio waves and magnets to create images of the inside of the breast. They are very sensitive and can detect even the smallest abnormality. In fact, they can be too sensitive. MRIs can generate “false positives;” incorrect positive diagnoses.

Nevertheless, MRIs are a powerful screening tool and can detect breast cancers that have not yet (or will not ever) cause lumps to develop. Like the previous image, this split screen shows an MRI on the left, and an illustration on the right. 

As cancer cells continue to grow into a tumor, it can spread to lymph nodes, clusters of infection-fighting structures that release white blood cells throughout the body to keep you healthy. These nodes filter out contaminants throughout the body, but with enough exposure, the cancer cells can spread to the lymph nodes and possibly to other parts of the body.

Breast cancer that spreads to other areas of the body is called “metastatic.” Metastatic cancer in lymphatic system can cause severe problems, including compromising your body’s ability to ward off disease, leaving you unable to fight off even the smallest infections. 

While breast cancer can affect many women, knowing your risk factors, the signs and symptoms, and other important details can help you with early detection—your strongest weapon against breast cancer. Explore more of Healthline's resources to learn more about the importance in remaining vigilant in the fight agains breast cancer.