What is breast cancer?

Breast cancer is a disease in which malignant (cancerous) cells are found in breast tissues. Each breast has 15 to 20 sections called lobes, which have many smaller sections called lobules. The lobes and lobules are connected by thin tubes called ducts.

Breast cancer is a type of cancer that grows in the breast. Women are much more likely to suffer from breast cancer than men are. It is the second most common type of cancer and the second leading cause of cancer death for U.S. women.

Breast cancer is a malignant tumor that starts from cells of the breast. A malignant tumor is a group of cancer cells that may grow into (invade) surrounding tissues or spread (metastasize) to distant areas of the body. The disease occurs almost entirely in women, but men can get it, too.

The normal breast

To understand breast cancer, it helps to have some basic knowledge about the normal structure of the breasts.

The female breast is made up mainly of lobules (milk-producing glands), ducts (tiny tubes that carry the milk from the lobules to the nipple), and stroma (fatty tissue and connective tissue surrounding the ducts and lobules, blood vessels, and lymphatic vessels).

Most breast cancers begin in the cells that line the ducts (ductal cancers). Some begin in the cells that line the lobules (lobular cancers), while a small number start in other tissues.

Stuart A. Linder, MD
Plastic Surgery

Breast cancer is the transformation of cells into a malignant tumor.  These tumors can become metastatic and spread or invasive and move into surrounding tissues.  Breast cancer cells continue to duplicate and replicate, which can create a tumor, which can subsequently spread to other parts of the body.  Metastatic tumors of the breast can spread to the lungs, liver and bone.  Diagnostic testing and biopsies, as necessary, should be performed in order to determine benign versus malignant tumors.

Breast cancer is cancer that forms in cells of the breast. The breast consists of lobules (glands that make breast milk), ducts (small tubes that carry milk from the lobules to the nipple), fatty and connective tissue, blood vessels and lymph vessels.

The milk-producing ducts and glands are the two most likely areas to develop cancerous cells. In rarer cases, breast cancer begins in fatty tissues, also known as stromal tissues. Breast cancer may also occur in surrounding lymph nodes, especially those of the underarm.

Breast cancer, the uncontrolled growth of cells in the breast, is the most common type of cancer among women, excluding skin cancer. Breast cancer forms in the tissues of the breast, usually the ducts (tubes that carry milk to the nipple) and lobules (glands that make milk). It occurs in both men and women, although male breast cancer is rare.

Cancer begins when cells in a particular location of the body start to grow out of control, locally invade other tissues, relocate to other parts of the body, replace normal tissues, or grow and form new tumors. There are many types of cancer and breast cancer is one of them. In most cases, the collection of these unregulated cells with unpredictable growth cycles may form a precancerous lesion or tumor that may initially appear benign but eventually may grow beyond normal boundaries, overrun surrounding tissues, enter into the blood or lymphatic systems, and spread to distant areas of the body via the process called metastasis.

First off, most breast lumps are not cancerous. Most lumps are caused by benign fibrocystic disease, but may still need to be biopsied to rule out cancer. Some common changes in the tissue of the breast may be felt as lumps due to the formation of fibrous scar-like tissue and cystic fluid-filled sacs. There are also many non-cancerous growths that are benign non-life-threatening tumors that do not spread outside the breast tissue to other organs, like fibroadenomas or intraductal papillomas.  

“Ductal carcinoma in situ” of the breast may be referred to as “non-invasive” or “pre-invasive” breast cancer. This naming system describes an early stage of cancer, when cells are confined to the layer of cells where they began. When cancer cells are confined to the lobules it may be called “Lobular Carcinoma In Situ”, which is actually neither a pre-cancerous lesion or true cancer in and of itself. 

An invasive cancer describes unrestricted cell growth beyond the layer of tissue from which it started. Nearly all breast cancers are invasive or infiltrating carcinomas, either invasive ductal carcinoma or invasive lobular carcinoma. Invasive ductal carcinomas and invasive lobular carcinomas stem from the unregulated growth of cells that line the tubes that relay milk to the nipple or collect milk in lobules. Some breast cancers are adenocarcinomas that originate from the cells in milk-producing glandular tissue that make and secrete breast milk. Less often, there are stromal cancers that originate from connective tissues such as muscle, fat, or blood vessels called sarcomas, lipomas, angiosarcomas or angiofibromas.

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.