A mammogram may be ordered to investigate a lump that has been found during a physical examination of the breasts, either by the patient herself, or by her doctor. However, women are being urged to have routine mammograms since it is the only reliable method of detecting cancer at the earliest possible stage, even before a lump can be felt. Unfortunately they are not 100% reliable, and a mammogram should always be preceded or followed by a breast examination by a doctor.
Cancer cells are denser than ordinary cells and are impenetrable to certain X-rays. A tumour will therefore appear as a white patch on the mammogram picture. Mammography can sometimes detect the difference between benign and malignant tumours.
The rate of breast cancer rises markedly in women above 50, and regular mammograms are recommended for all women over this age, generally once every two years. Women younger than this should have regular mammograms if there is a high risk of developing breast cancer. Studies carried out in various parts of the world estimate that the death rate from breast cancer is reduced by up to 70% in screened women.
To have a mammogram, the woman will strip to the waist and sit or stand in front of a small table, leaning in such a way that her breast is resting on the table, where it will be placed in various positions and photographed by the X-ray machine above. The breasts will be compressed to reduce the distance the X-rays must pass through them, and to reduce distortion caused by the curvature of the breast surface. The technique is especially valuable in the examination of large breasts, because the contrast is greater. However, a trained radiologist will detect any abnormalities in even the smallest breasts.
Having a mammogram is painless, although some women find the compression of their breasts uncomfortable. For routine mammograms, it is better to make the appointment in the first two weeks of the menstrual cycle when the breasts are not swollen and painful because of normal hormonal changes.
Modern mammography equipment delivers very little radiation and so is considered safe. Nevertheless, even small amounts of radiation increase the likelihood of getting cancer to a degree, and this needs to be taken into account when deciding on the frequency of routine tests. The older a woman gets, the less she is at risk from radiation, so those for whom a mammogram is of most value are at least risk from exposure to radiation. If an abnormality is detected, it may be further investigated by an ultrasound and biopsy.