Breast cancer: What is it and what are the causes?

One woman is diagnosed with breast cancer every three minutes, and four women will die every hour. It is the most common cancer among women of all ages and, though more likely to afflict women, over 2,000 men will be diagnosed with breast cancer in 2008. A woman’s chance of developing breast cancer increases with age, but as recently witnessed with Christina Applegate’s fight with breast cancer, being young does not make you immune to this potentially fatal disease. Your best defense is awareness and education – read on to learn more about breast cancer and see if you are at risk.

What is breast cancer?

Breast cancer is a malignant tumor that starts from cells of the breast. There are different types of breast cancer, and some tumors can be a mix of these types.

Understanding your breasts can help you better understand how cancer can affect them. Your breasts are made up of milk-producing sacs, passageways for carrying milk, supporting tissue, lymph nodes, glands, tiny muscles and fat. Throughout your life, due to hormones, age and weight, not only does the appearance of your breasts change but also their composition and functioning.

According to the American Cancer Society (ACS), most breast cancers begin in the cells that line the ducts (called ductal cancer), some begin in the lobules (referred to as lobular cancer), and a small number start in other tissues.

When cells in your breast grow and divide out of control, they form lumps — sometimes benign (without cancer) and sometimes malignant. The cells of malignant tumors spread into nearby tissue, called invasion, as well as into other parts of the body via the lymph and circulatory systems, better known as metastasis.

Different types of breast cancer

Carcinoma in situ

Nearly all breast cancers are carcinomas — either ductal or lobular (in the milk-making glands). In this type of breast cancer, cancer cells invade the lining of the breast — characteristically the early stage of cancer when it is isolated in the layer of cells where it began.

The ACS says that with breast cancer, in situ means that the cancer cells are only in the ducts (ductal carcinoma in situ) or lobules (lobular carcinoma in situ) and that they have not spread into deeper tissues in the breast or to other organs in the body. Ductal and lobular carcinomas in situ are sometimes referred to as non-invasive breast cancers.

Nearly all women with ductal carcinoma in situ can be cured. Women with lobular carcinoma in situ are at risk of developing more aggressive cancers. Both of these cancers can be detected with mammograms and, if detected early, can be successfully treated.

Invasive (infiltrating) carcinoma

Most breast cancers are invasive carcinomas, either invasive ductal carcinoma or invasive lobular carcinoma. An invasive cancer is one that has already grown beyond the layer of cells where it began.

Invasive ductal carcinoma is the most common breast cancer (accounting for eight of 10 breast cancer cases), starting in a milk passage or duct and breaking through to invade other breast tissue as well as other parts of the body.

Invasive lobular carcinoma is a cancer that starts in the milk glands or lobules but can then spread to other parts of the body. It accounts for about one in 10 invasive cancers.

Inflammatory breast cancer

An uncommon type of invasive breast cancer, inflammatory breast cancer usually has no lump or tumor, and makes the skin of the breast look red and pitted and feel warm. The breast can also become larger, firmer, tender or itchy. This type of invasive cancer accounts for about one to three percent of all breast cancers.

The ACS warns that in its early stages, inflammatory breast cancer is often mistaken for infection. Because there is no defined lump, it may not show up on a mammogram, which may make it even harder to catch early. It usually has a higher chance of spreading and a worse prognosis than invasive ductal or lobular cancer.

What are the primary causes of breast cancer?

Though there are many theories on the causes of breast cancer, the etiology of the disease remains an enigma. It is known that changes in a woman’s DNA can cause a healthy breast to develop cancer — these changes can be inherited or acquired.

Though inherited DNA changes can increase your risk of developing cancer and are responsible for the cancers that run in some families, most breast cancer DNA changes happen during a woman’s life — these are called acquired changes, and most breast cancers have several of these acquired gene mutations. These DNA changes are not within your control.

There are risk factors that are certainly linked to cancer, and some of them are within your control to change. The risk factors you cannot change include:

• Gender: Breast cancer is 100 times more common in women than men.
• Age: Your chance of cancer goes up with age.
• Genetic risk factors: Five to 10 percent of breast cancers are thought to be from inherited mutations.
• Family history: You are at an increased risk if you have blood relatives with breast cancer. However, according to the ACS, 70 to 80 percent of women who get breast cancer do not have a family history of this disease.
• Previous breast cancer: If you have had breast cancer in one breast, you are at a higher risk of getting a new cancer in either breast.
• Race: Though white women are more likely to get breast cancer, African American women are more likely to die from it.
• Dense breast tissue: Dense breast tissue can make it harder to detect breast cancer, and having more glandular tissue and less fatty tissue can increase your risk.
• Hormones: You are at an increased risk if you started your period before age 12 or went through menopause after age 55 — having more periods increases your exposure to estrogen and progesterone, hormones that have been associated with breast cancer.