I.

Introduction

Mammogram, X-ray image of the breast that helps physicians detect and evaluate breast abnormalities. Mammography is typically performed on women who do not have symptoms of breast cancer. The procedure can detect cancer in its early stages, when treatment is most effective. A mammogram can detect a breast abnormality as small as 0.5 cm (0.2 in), a size too small for a woman or her doctor to feel it as a lump.

II.

Taking a Mammogram

Technicians usually perform mammograms, and a medical doctor known as a radiologist interprets the image. The mammography procedure involves pressing the breast between two pieces of plastic to increase the amount of breast tissue exposed to X rays. The technician usually takes X rays of the breast from two different angles. Pressing the breast between two pieces of plastic may cause some women discomfort, but it does not harm the breast and, in fact, minimizes the necessary X-ray dose. The amount of radiation exposure received during mammography is about the same as that of a dental X ray.

The breast is composed of breast tissue and fat tissue. Breast tissue is relatively dense and appears white on a mammogram image. Fat tissue is less dense and appears gray to black on the image. Cancerous tumors are about the same density as normal breast tissue and appear as white spots on the mammogram. Tiny deposits of calcium sometimes appear as dustlike flecks on the image. These calcium deposits are usually harmless but are sometimes an early sign of cancer. An abnormal spot on a mammogram may also be one of a variety of benign conditions, such as a cyst (fluid-filled sac) or a fibroadenoma (benign tumor).

From 5 to 10 percent of all mammograms show some abnormality. Women who have an abnormal mammogram need to undergo further diagnostic tests to distinguish benign conditions from cancer. A doctor may recommend another mammogram to provide a magnified view of the breast abnormality or a clearer view of the suspect area. To distinguish a fluid-filled cyst from a solid mass (which may be either benign or cancerous), doctors may use ultrasound imaging of the breast. This test uses high-frequency sound waves to differentiate various types of tissue and is particularly helpful for examining fluid-filled structures. In some cases a fine needle aspiration or a biopsy of the abnormal area of the breast is necessary. For a fine needle aspiration, a physician uses a long needle to remove fluid and cells from the breast lump. In a biopsy, a scalpel is used to remove part or all of the abnormal tissue. The cells or tissue are then examined under a microscope to determine if cancerous cells are present.

Mammograms are performed in a variety of settings, including doctor’s offices, hospital radiology departments, and mobile vans. All mammography providers must be accredited by the Food and Drug Administration (FDA). The cost of mammography is covered by Medicare (the federal health insurance program for the elderly) and most private health insurance plans. A program run by the United States Centers for Disease Control and Prevention (CDC) provides free or low-cost mammograms to low-income women who do not have health insurance.

A.

Accuracy of Mammography

Although most scientists agree that mammograms are useful in detecting breast cancer, the procedure is not foolproof. Mammograms do not always find breast cancer when it is present. Scientists estimate that mammograms miss about 25 percent of breast cancers in women 40 to 49 years old and about 10 percent of breast cancers in older women. Furthermore, an abnormal mammogram does not necessarily indicate the presence of breast cancer. In fact, only about 3 percent of women aged 40 to 49 years and 12 percent of women aged 50 to 69 years who have an abnormal mammogram result turn out to have breast cancer. In the remaining cases, what appears abnormal on a mammogram is later identified as benign or normal tissue.

Some experts have raised concerns about the imprecision of mammography and the potential harm that a misleading result may cause. A normal mammogram result in a woman who has breast cancer may falsely reassure her, causing her to become less vigilant about breast cancer screening. An abnormal mammogram result in a woman who turns out not to have breast cancer may cause her to undergo unnecessary surgical biopsies and other diagnostic tests. Further, women may experience great anxiety about having an abnormal mammogram result even after being told that they do not have cancer.

Several studies have shown that regular mammograms decrease deaths from breast cancer in women aged 50 to 69 if the women receive appropriate treatment after the cancer is detected. Studies about the effectiveness of mammograms in preventing breast cancer deaths among younger women, aged 40 to 49, are not so clear-cut.

III.

Mammography Recommendations

Despite conflicting results about the effectiveness of mammography in preventing deaths in younger women, the United States Preventive Services Task Force, an independent panel coordinated by the Department of Health and Human Services, recommends that women have a screening mammogram every one to two years beginning at age 40. The American Cancer Society also recommends that women over age 40 have a mammogram every year. Most doctors agree, however, that if a woman has a family history of breast cancer, she should begin mammography at an earlier age. Many medical authorities recommend combining mammography with other forms of breast cancer screening, such as breast self-exams and clinical breast exams performed by a physician or other health-care provider, although scientific studies have not shown that these forms of screening prevent breast cancer deaths.

Scientists first began to recognize the usefulness of mammography in detecting breast cancer around 1960. However, mammography did not become widely used for breast cancer screening in the United States until the 1980s. As mammography became more widespread, several studies showed that the quality of mammograms varied greatly at different centers that performed the test. To address these problems, Congress passed the Mammography Quality Standards Act (MQSA) in 1992. This legislation sets standards for mammography equipment, image quality, record keeping, and staff qualifications to help ensure that high-quality mammography is available to women everywhere in the United States.