Breast health

What is breast cancer?

To combat breast cancer effectively, it's important to first understand just what breast cancer is, how it occurs, the stages of the disease, and how these affect you. Equally important is dispelling many of the myths and misunderstandings surrounding breast cancer and women's risk of the disease.

The anatomy of the breast

Let's first examine the anatomy of the breast. The breast, or mammary gland, contains lobules, glands which produce milk, ducts which connect the lobules to the nipple, and stroma, fatty tissue and connective tissue surrounding the ducts and lobules; blood vessels, and lymphatic vessels. As we'll see a little later, most breast cancers begin in the ducts (atypical ductal hyperplasia), some in the lobules (lobular carcinoma in situ), and the rest in other tissues.

Image by illustrator Susan Spangler appears with the artist's permission
and courtesy National Cancer Institute, U.S. National Institutes of Health.

Lymphatic vessels are quite similar to blood vessels except that rather than carrying blood, lymphatic vessels carry lymph, a clear fluid that contains tissue fluid, waste products, and immune system cells. Small, bean-shaped collections of immune system cells found along lymphatic vessels, lymph nodes can be invaded by cancer cells which have entered lymphatic vessels and metastasized (spread) to involve them as well.

Most lymphatic vessels in the breast connect to axillary lymph nodes under the arm, while others connect to internal mammary nodes in the chest or to supra- or infraclavicular nodes above or below the clavicle (collarbone), respectively.

What is breast cancer?

As with all cells in the human body, breast cells have a life cycle during which they grow, divide, produce more cells and eventually die. Cells' life cycle is controlled by genes in their nucleus. Under normal conditions, genes are able to effectively regulate this cellular life cycle. However, when genes develop an abnormality, the life cycle is affected and some cells may continue to divide even when new cells are not needed, forming a mass of new issue called a growth or tumor.

Tumors may be benign or malignant.

Benign tumors are not cancerous and can be removed. While they are abnormal growths, benign tumors such as fibroadenomas or papillomas are not cancerous and cannot spread beyond the breast to affect other organs. Such benign growths are not life threatening.

The majority of breast lumps are benign and are often the result of fibrocystic changes that may cause swelling and pain. Such changes are quite common just before a woman's menstrual period is about to begin, with breasts feeling nodular or lumpy. This can occasionally be accompanied by a clear or slightly cloudy nipple discharge.

Malignant tumors, on the other hand, are cancer. Breast cancer, therefore, is an uncontrolled growth of breast cells. Cells in such tumors divide without any rhyme or reason, invading nearby tissues and organs. Through a process known as metastasis, cancer cells can also break through normal breast tissue to other parts of the body.

For instance, breast cancer may metastasize from breast tissue to reach the axillary lymph nodes under the arm. When this happens, cancer cells may continue to grow, causing the underarm lymph nodes to swell. Once breast cancer cells have spread to the axillary lymph nodes, they are more likely to metastasize to other organs of the body as well. This is why, when choosing a breast cancer treatment, it's especially important to find out if breast cancer has spread to the axillary lymph nodes.

Let's examine the types of breast cancer, since an understanding of the terms used will help you learn how cancer patients vary in their prognosis and treatment.

Types of breast cancers

Because nearly all breast cancers begin in the ducts or lobules—glandular tissues—they are called adenocarcinomas. Adenocarinomas may be classed as ductal carcinomas or lobular carcinomas.

Confined to the immediate area where it began, in situ refers to an early stage of cancer. When used in reference to breast cancer, in situ denotes cancer that remains confined to ducts (ductal carcinoma in situ) or lobules (lobular carcinoma in situ). In other words, this cancer has not invaded fatty tissues in the breast, nor has it metastasized to other organs in the body.

Also known as intraductal carcinoma and comprising approximately 20 percent of new breast cancer cases, ductal carcinoma in situ (DCIS) is the most common type of non-invasive breast cancer. In DCIS, cancer cells are inside the ducts but have not spread beyond the duct walls into surrounding breast tissue. Mammography is the most effective and reliable means of finding DCIS early. What's more, nearly all women diagnosed at this early stage can be cured. Yet, an important distinction the pathologist will need to make is noting whether tumor necrosis, an area of dead or degenerating cancer cells, exists. If necrosis is present, the tumor is considered more aggressive and is described as comedocarcinoma.

Although sometimes classified as a non-invasive breast cancer, lobular carcinoma in situ (LCIS) is not a true cancer. LCIS begins in the milk-producing glands, but does not spread beyond the wall of the lobules. Despite many breast cancer specialists' belief that LCIS itself does not become an invasive cancer, it should be noted that women with LCIS do have an increased risk of developing an invasive breast cancer in the same or even in the opposite breast. Therefore, women with LCIS should undergo a physical exam 2 to 3 times per year, in addition to a yearly mammogram.

The most common breast cancer, comprising approximately 80 percent of invading breast cancers, infiltrating (or invasive) ductal carcinoma (IDC) begins in the duct of the breast. Called invasive because it has broken through the wall of the duct and invaded nearby fatty breast tissue, IDC can metastasize to other parts of the body through the lymphatic system and bloodstream.

Beginning in the lobules and metastasizing to other parts of the body, infiltrating (or invasive) lobular carcinoma (ILC) comprises about 5 percent of all invasive breast cancers and is harder to detect through mammography than infiltrating ductal carcinoma.

A rare type of invasive breast cancer that constitutes between 1 and 3 percent of all breast cancers, inflammatory breast cancer starts in the breast ducts and spreads to the skin of the nipple and then to the areola (the dark circle around the nipple).

Developing under the connective tissue of the breast, phyllodes tumor is extremely rare. Although benign in most cases, phyllodes (also spelled phylloides) can also, on rare occasions, be malignant. When benign, phyllodes are removed along with a narrow margin of normal breast tissue. In cases of malignant phyllodes, the tumor is removed along with a wider margin of normal breast tissue and may also be removed by mastectomy.

Who's at risk?

There are identified risk factors that may place certain women at significantly greater risk of breast cancer. In addition, having one risk factor—or even several—does not necessarily mean you will develop breast cancer. Understanding risk factors places you in a far better position to understand and manage your risk profile and to discuss it with your doctor. Risk factors include:

Gender

Every woman is at some risk of developing breast cancer—that's a sad fact of being a woman. Although breast cancer does affect men, it is 100 times more common among women. This is because, obviously, women have more breast cells than men do. It may also be due in part to the fact that women's breast cells are constantly exposed to the growth-promoting effects of female hormones.

Age

According to Breastcancer.org, the chances of developing breast cancer before the age of 39 are slim indeed. From birth to age 39, 1 in 231 (less than 0.5%) women will develop breast cancer. However, from ages 40 to 59, risk increases to 1 in 25, or 4%, and from ages 60 to 79, the chance of developing breast cancer is 1 in 15, nearly 7%. Put another way, this means that about 18 percent of cancer diagnoses are among women in their 40s and that about 77 percent of women are in their 50s when they are diagnosed.

The Canadian Cancer Society states that:

Personal history

Women who have already had breast cancer are 3 to 4 times more likely to develop new occurrences of the disease. Risk is estimated at 1 percent per year, which means that over the course of ten years, if a woman has had breast cancer before, she has a 10 percent chance of developing it again. Medications, however, can help reduce this risk.

Family history

Women with a family history of breast cancer are also at increased risk of the disease. This is especially true if a direct first-degree relative (mother, daughter, sister) on either her mother or father's side has had breast cancer: risk nearly doubles when this is the case. Risk is also higher among women belonging to families in which multiple generations of family members were affected by breast or ovarian cancer, in which a family member was diagnosed with breast cancer at a young age (under the age of 50), or in which a family member (male or female) was affected by breast cancer in both breasts.

Consider the following:

One should also not assume that breast cancer runs only in families and that if no one in her family is affected, she will likely not develop breast cancer. The truth is that nearly 80 percent of women who develop breast cancer have no known family history of the disease. Of women who do have a family history of breast cancer, their personal risk may be increased slightly, significantly, or not at all.

Recent evidence shows that about 10 percent of breast cancer cases are hereditary as the result of gene mutations such as those affecting the BRCA1 and BRCA2 genes. Normally, these genes help prevent breast cancer by making proteins that keep cells from growing abnormally. However, if a mutated gene is inherited from either parent, a woman's risk of breast cancer increases: women with an inherited BRCA1 or BRCA2 mutation have a 35 to 85 percent chance of developing breast cancer.

Genetic evaluation typically includes detailed assessment of a woman's family history, and genetic counseling may include blood tests for the breast cancer gene mutations mentioned above. While such tests do not predict whether a woman will develop breast cancer, they do indicate whether she has inherited a BRCA1 or a BRCA2 mutation.

Many women who inherit such breast cancer gene mutations never develop breast cancer: of women with a BRCA1 (located on chromosome 17) or BRCA2 (located on chromosome 13) inherited genetic abnormality, 40 to 80 percent will develop breast cancer over their lifetime while 20 to 60 percent will not. It also follows that a woman who has not inherited a gene mutation from either parent cannot pass it on to her children.

Race

Caucasian women are at slightly higher risk of developing breast cancer than Black women. Yet Black women are more likely to die of breast cancer because their cancers are often diagnosed later and at an advanced stage. There is also some speculation that black women may have more aggressive tumors. Asian, Hispanic/Latino, and Aboriginal/First Nations women appear to have a lower risk of developing breast cancer. Also worth noting is that hereditary breast cancer is more common in Jewish women than in non-Jewish women.

Prolonged, uninterrupted exposure to estrogen

Breast cell growth is stimulated by the presence of estrogen, whether estrogen produced naturally in the body, or estrogen introduced as part of estrogen replacement therapy. Early menarche (menstruation which began before age 12) and late menopause (menopause after age 55) are each synonymous with a greater number of years during which the body produced estrogen. As a result, women who got their period early or who entered menopause late are at increased risk of developing breast cancer.

Post-menopausal women who have been prescribed estrogen alone or in combination with progesterone for periods of five years or longer are also shown to be at increased risk for breast cancer. It's also been suggested that estrogen and progesterone combined may increase the risk of dying of breast cancer.

Women who have had their first full-term pregnancy after the age of 30 are also at increased risk because their bodies have had more years of producing estrogen without breaks from regular menstrual cycles.

Obesity

Obesity is associated with an increased risk of breast cancer, particularly in post-menopausal women. Women who are overweight experience increased production of estrogen outside their ovaries, and this in turn contributes to increased levels of estrogen throughout the body.

Alcohol

Alcohol consumption in excess of two drinks per week also appears to increase risk since alcohol limits the liver's ability to regulate blood estrogen levels. Research suggests that those who have 2 to 5 drinks daily are 1.5 times more likely to develop breast cancer than those who do not drink. What's more, alcohol is also known to increase the risk of developing cancers in the mouth, throat, and esophagus.

Changes in breast cells

Changes in breast cells, identified when a breast biopsy is performed, can also increase risk of breast cancer. Such cellular changes may be identified as being either atypical ductal hyperplasia or lobular carcinoma in situ. Atypical ductal hyperplasia refers to overproduction of cells lining the breast ducts, whereas lobular carcinoma in situ refers to an uncontrolled growth of lobular cells.

Previous breast biopsy

Women whose earlier breast biopsies showed proliferative breast disease without atypia or usual hyperplasia are 1.5 to 2 times more likely to develop breast cancer than other women, while those whose previous biopsies showed a result of atypical hyperplasia are 4 to 5 times more likely to develop breast cancer. Biopsy specimens diagnosed as fibrocystic changes without proliferative breast disease do not affect breast cancer risk.

Previous breast radiation

Those women who, whether as children or young adults, have had previous radiation therapy to the chest area as treatment for cancer (e.g. Hodgkin's lymphoma) have a significantly increased risk of breast cancer. Some reports have suggested the risk is 12 times greater than normal, although the risk varies depending on the age of the patient at the time of radiation treatment: younger patients have a higher risk. However, if chemotherapy was given, risk is reduced because chemotherapy often stops ovarian hormone production.

Physical activity

There is yet another benefit to regular exercise: recent studies show that strenuous exercise in young women may provide long-term protection against breast cancer. In addition, moderate to strenuous physical activity in adulthood is also believed to lower breast cancer risk.

Breastfeeding

There are studies which suggest that breastfeeding may slightly decrease breast cancer risk, particularly if breastfeeding continues for 1.5 to 2 years. Yet other studies suggest there is no correlation between breastfeeding and breast cancer risk.

Even if you believe you are at high risk of developing breast cancer, do not resign yourself to thinking there is little or nothing you can do. It's true that there is nothing that can be done to prevent breast cancer from occurring, but there are things that may be done to reduce one's risk. Lifestyle changes such as stopping smoking, exercising regularly, minimizing alcohol consumption, and taking medications such as tamoxifen (Nolvadex) can all help reduce the risk of breast cancer in women at high risk. In cases of very high risk, prophylactic mastectomies may be recommended. Be sure to discuss your concerns with your doctor before making any assumptions about your personal risk.

Myths about breast cancer

Breast cancer is often believed to affect only older women. As we've seen, breast cancer can affect women at any age, although having one or more of the above-mentioned risk factors does not necessarily imply that a woman will develop breast cancer.

Another common misconception is that use of antiperspirants or oral contraceptives increases breast cancer risk. There is no evidence to support that antiperspirants increase breast cancer risk. Higher-dose pills of yesteryear were associated with a slightly increased risk of breast cancer. Today's birth control pills, however, contain estrogen and progesterone in low doses and have not been associated with increased risk of breast cancer; they have been clinically proven to provide some protection against ovarian cancer.

While monthly breast self-examination is recommended and ensures that a woman becomes familiar with the texture of her own breasts, BSE is not viewed as the best way to safeguard against or to detect breast cancer. By the time breast cancer can be felt in BSE, tumors are usually larger in size than those found through mammography. Therefore, the most effective and reliable way to detect breast cancer is through high-quality, film-screen mammography. Tactile breast examination by a doctor or gynecologist is said to find about 25 percent of breast cancers, while 35 percent are found through mammography alone. The best course of action is to use BSE or examination by your doctor (CBE) in combination with mammography as doing so is said to find 40 percent of breast cancers.

Not all breast cancers are fatal. In fact, the majority of cases (80 percent) of breast cancer have no signs of metastases. In other words, these patients' cancers did not spread beyond the breast and nearby lymph nodes. Survival rates for such cases are also encouraging: 80 percent of these cases live at least 5 years—most longer, and many much longer. Even in cases where metastases did occur, life expectancy and prognosis are good.

References

• What is Breast Cancer? American Cancer Society, Inc. (2004)
• What are the Risk Factors for Breast Cancer? American Cancer Society, Inc. (2004)
• Who Gets Breast Cancer? Breastcancer.org (2004)
• What Kind of Family History Suggests Hereditary Breast Cancer? Canadian Cancer Society. (2002–2004)
• Myths About Breast Cancer. Breastcancer.org (2004)
• Genetic Evaluation. Canadian Cancer Society. (2002–2004)
• Breast Cellular Changes. Breastcancer.org (2004)