Mammography

September 16, 2011

Breasts share the same basic structure. The mammary glands produce milk and are found in clusters throughout the breast. Ducts take the milk from the glands to the nipple during breastfeeding. Lymph nodes are present under the arm. The lymph nodes are small, normally bean-sized structures that help to fight infection and enlarge in the presence of infection or cancer in the breast tissue. There are reservoirs within the breast that store the milk. The areola is the part of the nipple that lubricates the nipple with oil. Fat in fibrous tissue surrounds the glands and ducts and gives the breast its smooth shape. Women who have more fat tissue in the breast have a softer breast, while having more fibrous tissue in the breast makes the breast feel firmer. Normally, a lump is easier to locate in a softer or more fatty breast, as compared to a firmer, dense breast.

At the time of each menstrual cycle, the drop in hormones results in a sloughing (breakdown) of the ductal lining. This lining regrows again in a cyclic fashion. The blood vessels around the ducts in other cells also undergo changes during the menstrual cycle. This causes the breasts, in some women, to become swollen, tender, denser, or lumpier in the week before menstruation. During pregnancy, the milk glands, ducts, areolae, and nipples enlarge. The breasts feel heavy, lumpy, and tender when nursing stops. Breasts usually return to their former size; however, they may be less firm. In many parts of the breast, the glandular growth remains until it reduces at the time of menopause. At the onset of menopause, there is a loss of breast tissue, structural components, and an increase in the fat. The milk glands and ducts shrink and the breasts become smaller and softer. The supporting ligaments lose some of their strength. It is important to note that the changes associated with the hormonal changes during a menstrual cycle are not uniform throughout the breast. This can cause some asymmetric findings on physical examination of the normal breast.

EPIDEMIOLOGY

As a result of widespread screening, breast cancer is the most commonly diagnosed cancer and the second leading cause of cancer deaths in women. The most common cause of death from cancer is lung cancer. Breast cancer in women under the age of 55 is an important cause of cancer death; however, half of all new cases and over half of the deaths occur in women over the age of 65 years. The estimated lifetime risk of developing breast cancer is now one out of every eight women.

RISK FACTORS FOR BREAST CANCER

The National Cancer Institute has developed a computer program that uses information to calculate a woman’s estimated risk of breast cancer. This program can be found on the institute’s website (http://cancertrials.nci.nih.gov).

Factors in the development of breast cancer include increased risk with increased age. The risk of breast cancer is greater with earlier onset of menarche (first menstrual period), which is the age that menstrual cycles begin. The age of the first live birth is important as the risk increases with later age of first pregnancy. Risk increases with the number of first-degree relatives with breast cancer. Prior breast biopsies, especially those showing atypical hyperplasia (abnormal cells on microscopic exam), help to predict an increased risk of breast cancer. Race is important as the risk is greater in white females. African American women have a lesser risk of breast cancer followed by Hispanic American women. Japanese American women have the lowest risk of breast cancer. It is important for all women to understand that all are at risk for breast cancer and that the majority of women with breast cancer have no identifiable risk factors. Other established risk factors include rare genetic problems that account for 5-10% of breast cancers. These are called BRCA-1 and BRCA-2 gene mutations. Risk factors for women with a personal history of breast cancer include a history of some specific breast cancers (ductal or lobular carcinoma in situ), or a history of receiving high-dose radiation therapy at an age of younger than 40. Late age at menopause is another risk factor.

WHAT IS A MAMMOGRAM?

A mammogram is an x-ray of the breast tissue. The mammogram is reviewed by a radiologist, and if he/she finds an abnormality, may recommend other examinations. The mammogram should be scheduled during the time that the breasts are less likely to be tender. This will help to ensure that it is a more comfortable experience. It is important not to use deodorant, powder, lotion, or perfumes on the breasts or under the arms. Mammography is a simple procedure. The woman undergoing the exam undresses from the waist up and the breast is positioned on the x-ray machine and placed between two flat pieces of plastic. The breast is pressed between the plates for a few seconds while the x-ray picture is taken. The pressure is slightly uncomfortable to many women; however, it does not harm the breasts. It is x-rayed from the side and from above. The complete examination takes about 15 minutes.

An ultrasound examination utilizes sound waves to produce an image of the breast tissue. It is used to evaluate whether a lump is a fluid-filled cyst or a solid lump. Fluid-filled cysts are not cancerous. Solid lumps may or may not be a cancer. The next step for a solid lump is usually a biopsy, where a small amount of the tissue or the entire lump is removed and analyzed. It is important to note that most lumps are not cancer.

The average mammogram delivers between 0.7 and 1 rad (x-ray units of measure), which is a minimal amount of radiation. This is about 10% of the exposure delivered 20 years ago. While there is a miniscule increased risk of cancer due to the radiation, the far greater risk is in missing a curable cancer at an early stage.

As in many fields of medicine, there is ongoing reassessment of the way that we look for early cancers, and breast cancer is no exception. The National Guideline Clearinghouse provides a guideline synthesis compiling all the major guidelines for breast cancer screening. The American Cancer Society, the American College of Radiology, and the U.S. Preventive Services Task Force recommend routine mammographic screening for women between the ages of 50 and 69 years. The U.S. Preventive Services Task Force recommends annual or biannual screening, while the American Cancer Society recommends annual screening. The screening should begin earlier in women with high risk for breast cancer (including those having relatives with breast cancer). The organizations that evaluate screening agree that there is no clear age at which mammography should be no longer offered to patients. However, this decision should be made on an individual basis, based on the person’s preference and her potential risks and benefits of the procedure. The main area of controversy is the mammographic screening of women between the ages of 40 and 49, who are at average risk for breast cancer. The American Cancer Society, the American College of Radiology, and the U.S. Preventive Services Task Force recommend routine screening in this age group. All three guideline groups acknowledged that the benefit of screening in women younger than 50 is weaker than the evidence for older women; however, they do support the screening. The recommended frequency of mammography in a woman in her 40s is every 1-2 years. This should be decided with her health care provider.

AT WHAT AGE SHOULD WE STOP GETTING MAMMOGRAMS?

Beyond the age of 70, the patient and her physician should make the decision. Frail elderly women with other life-limiting conditions may choose not to have this test performed.

Even though breast self-examination is not a proven way to screen for breast cancer, it is important to emphasize that women should be advised to report any breast changes that they may detect themselves to their physicians. It is important for the patient to look and feel for breast changes on her own.

BRCA-1 TESTING

In recent years, a breast cancer gene called BRCA-1 has been identified and it carries an 85% lifetime risk of breast cancer and a 60% risk of ovarian cancer. These familial breast cancer syndromes account for less than 1 in 10 breast cancers. Even in women with several family members with breast cancer, routine screening for BRCA-1 is negative more than 90% of the time. BRCA-1 gene testing is not indicated in everyday practice, as there are no long-term data to support its use.

SEE ALSO: Breast cancer, Breast examination, Breast-feeding, Breast lumps, Lactation, Mastectomy

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