Mammography

• Mammography has been used for over 30 years and has the potential to save lives by diagnosing early cases of breast cancer, the most common form of cancer in women.
• Mammography is a special type of low dose X-ray imaging of the breast to create detailed soft tissue images.
• The low dose ionising radiation and filters are used to produce high contrast, high resolution images which can demonstrate microcalcifications smaller than 100 μm.
• Two recent enhancements have been developed:
  • Digital mammography or full-field digital mammography (FFDM). This is similar from the patients' perspective but uses solid state detctors rather than x-ray film. These convert x-rays into electrical signals. The images produced are viewed on a computer screen but can be printed out to look like conventional mammograms. The detection of mammographic lesions is the same as with the conventional technique.¹
  • Computer-aided detection (CAD). Digital or conventional mammograms can be processed by computer to highlight abnormal areas of density, mass or calcification. Such areas may then be further analysed.
• It is used for screening in asymptomatic women for early detection of breast cancer (on average detecting 75% of cancers at least 1 year before they can be felt).
• It is also used diagnostically in symptomatic women and because of the extra images and time involved in diagnostic mammography it is more expensive than screening mammography.

Screening can be divided into:

• Screening of the general population. The UK's NHS breast screening programme was started in 1987 after the Forrest Committee Report.^{2 3} This recommended:
  • 3 yearly mammography for all women aged 50-70 years using single oblique view mammography.
  • Recall of all patients with abnormalities to specialist assessment units. These allow further investigation with:
    • Clinical examination.
    • Special view mammography.
    • Ultrasound examination (useful in younger patients and to identify cysts particularly).
    • Fine needle aspiration and cytology.
  Strategies for increasing uptake of breast cancer screening have been the subject of a Cochrane review.⁴ Simple measures such as mailing of information are effective. Some more expensive interventions involving home visits were not. There is a role for practices in encouraging and facilitating uptake backed up with computerised recording of mammography results and appointment reminders.
  In the United States the recommendation from various groups (American College of Radiology, American Cancer Society, American Medical Association, US Department of Health and Human Services) is for screening mammography annually starting at age 40.^{5 6}
• Screening in special groups. Some special groups may need additional and/ or earlier screening. NICE guidance for familial breast cancer has been produced.⁷ Such groups include:
  • Patients who have had breast cancer.
  • Patients who have a strong family history of breast cancer.
  • Patients who have a relevant genetic history. Three genes have been identified which predispose women to breast cancer- BRCA1, BRCA2 and TP53. NICE guidance has been issued.⁷

Diagnostic mammography may be performed in:

• Patients with abnormal clinical findings (for example breast lumps).
• After an abnormal screening mammogram.

Techniques used include:

• Obtaining different views to localise abnormalities.
• Localisation to facilitate guided biopsy.
• Imaging of ducts using ductography.
• Imaging of lumpectomy tissue to confirm targeted tissue has been removed.

• Referral information. Most specialist breast screening units will have a specific referral form requesting relevant information and with diagrams to assist description of examination findings. These include information on:
  • Urgency of the referral.
  • Breast symptoms including lumps, pain, discharge.
  • Breast examination findings including lumps (diagram to show size, position, consistency)
  • Lymph node examination particularly axillary.
  • Relevant past history of any breast disease both benign and breast cancer. Note that although breast implants can impede accurate mammography it is still possible to perform mammography in patients with implants.
  • Menstrual history.
  • Medication especially any hormones.
  • Family history particularly of breast cancer.
• Advice to patients:
  • The best time for a mammogram is one week after menstruation as the breasts are usually less tender. The week before menstruation should be avoided.
  • Do not wear talcum powder or deodorant as these can produce calcium spots.
  • Any previous mammograms should be made available to the radiologist to help interpretation.
  • Ensure that instructions on notification of results are clear and understood.
  • Advise of risks:
    • False positive results. 5 to 15% of screening mammograms require more testing (further views on mammogram or ultrasound).
    • False negatives. 5% of palpable carcinomas are not detected on mammography.
    • Successive mammograms incur cumulative carcinogenic radiation.
    • Mammography is less accurate in young women under age 35 who have dense breast tissue.
• Explanation of the procedure. This should include a brief description of what is involved. It can involve discomfort because of the compression of the breast tissue between plastic paddle and platform. If necessary less compression can be used to reduce discomfort.

This should only be underatken by appropriately trained radiologists. The radiological classifications are aimed at improving diagnostic consistency and accuracy.⁶

The programme in the UK has screened more than 19 million women and detected around 117,000 cancers. The latest research shows that the NHS breast screening programme saves 1400 lives every year in England.³

GPs have an important role in the NHS Breast Screening Programme. Diagnostic mammography should be part of appropriate and expert management of clinical findings or symptoms and will usually be done with referral to an appropriate breast specialist.