Publication of the Forrest Report ⁵ on breast screening and the subsequent implementation of the NHSBSP revolutionised mammography in the UK. The report made numerous recommendations: projections that should be undertaken on each breast; the screening interval; interpretation of the mammograms; assessment and follow-up; and implementation of quality assurance and quality control procedures at every step of the programme. Recommendations regarding the setting up of an advisory committee and the Pritchard Report¹² then led to guidance on quality issues. Recommendations made in the Forrest and Pritchard Reports do not pertain only to screening mammography services, as they are pertinent wherever mammography is offered, thus ensuring equity of provision for all women.

Breast disease demonstrated with mammography

Benign breast conditions

There are a number of benign breast conditions that may manifest on mammograms. Some examples are:

• Benign breast change: There is no evident disease process and changes are often brought about by hormonal variations. Conditions such as mastitis and fibroadenosis would come under this umbrella.

• Cysts: Cystic changes in the breast are very common and, as with most benign breast conditions, tend to be bilateral.

• Fibroadenoma: These are often found incidentally as they are usually too small to feel. Larger lesions occur in younger women. Fibroadenomas in postmenopausal women do not grow (except in women on hormone replacement therapy) and new lesions seldom appear.

Benign breast conditions and their mammographic appearances

Cysts	Visualised as an increase in density usually with smooth edges
Fibroadenoma	Has no specific characteristic features but is usually smooth, rounded, well defined, and causes displacement of the surrounding tissues. When calcification occurs the lesion is said to have a ‘popcorn’ appearance

Breast cancer

United Kingdom breast cancer facts and statistics:¹³

• Breast cancer is the most common cancer in women

• The lifetime risk of developing cancer of the breast is 1 in 8

• 80% of breast cancers occur in postmenopausal women

• 5–10% of breast cancers are hereditary

• 90% of breast lumps are benign

• Around 300 men are diagnosed in the UK each year

• Breast cancer can be divided into two main types:

In situ carcinoma: this is contained within the breast ducts or lobules, although it has the potential to become invasive

Invasive carcinoma: this has spread from the ducts or lobules into the surrounding breast tissue. It has the potential to metastasise, via the blood or lymphatic systems, to other parts of the body and may ultimately shorten the patient’s life. Invasive cancers are graded histologically from 1 to 3, according to how similar the breast cancer cells are to normal cells of the same type. The higher the grade the more different the cancer cells are from normal cells and the more rapidly they reproduce ¹⁴

Cancer type and mammographic appearance

Cancer type	Appearance
DCIS	Microcalcifications
Invasive ductal carcinoma	Usually spiculate mass, but often has calcification and parenchymal distortion
Invasive lobular carcinoma	Similar to ductal carcinoma but microcalcification is less common

Mammography is often not able to distinguish between benign and malignant masses, which is why breast imaging services do not stop at mammography but incorporate other imaging modalities such as ultrasound and magnetic resonance imaging (MRI). However, it is possible to make some general observations from mammographic appearances:

• A spiculated mass with microcalcifications is highly suspicious and strongly indicates malignancy; any mass with distortion should be assumed to be malignant until proved otherwise

• Microcalcifications are difficult to evaluate but could represent DCIS

• Well-defined masses are likely to be benign

Dose implications for the breast undergoing mammography

It is important to remember that mammography uses radiation and therefore has the potential to induce carcinoma by the biological effects of radiation. The risk is considered to be low for the patient undergoing a single mammogram because the dose is well below the threshold for deterministic effects, and the reproductive cells are not exposed to primary radiation. Risks are highest in young women and are estimated to range from 9.1 fatal carcinomas induced per million per mGy in the 30–34-year age group, falling to 7.5 fatal carcinomas induced per million per mGy in the 45–49-year age group and 4.7 fatal carcinomas induced per million per mGy in the 60–64-year age group.¹¹

For women of screening age in the UK the risk of radiation-induced breast cancer (including non-fatal tumours) is approximately 1 in 100 000 per mGy. Radiation dose for women attending the NHSBSP is taken to be on average 4.5 mGy per two-view screening examination. The risk of radiation-induced cancer for a woman attending mammographic screening (two views) by the NHSBSP is about 1 in 20 000 per visit, and it is estimated that about 170 cancers are detected by the NHSBSP for every cancer induced.¹⁵

Digital mammography

The NHSBSP approved the use of digital mammography for breast screening following the results of the Digital Mammographic Imaging Screening Trial (DMIST), which enrolled almost 50 000 women. Each woman in the trial underwent both film mammography and digital mammography and various factors were recorded, such as the age of the woman, density of the breast, thickness of the compressed breast, and radiation dose. Digital and film mammograms were reported separately before being compared, and it was determined that the sensitivity of film mammography was comparable to that of digital mammography in women with fatty breasts. However, in women with dense breasts the trial demonstrated significantly improved sensitivity of digital mammography over film mammography. Furthermore, the trial revealed that the radiation dose with digital mammography was 22% less than with film mammography.¹⁶ In 2007 the Department of Health stated that all screening units should have at least one digital mammography set by 2010.¹⁷

Alternative and complementary imaging techniques

Nuclear medicine

There are two main uses of nuclear medicine in breast imaging:

1 Sentinel node biopsy. This involves the use of technetium-labelled colloid to label the first axillary lymph node to drain the breast – the sentinel node. If this node is metastasis free then axillary clearance can be avoided. Sentinel node status is able to accurately predict axillary lymph node status in over 95% of cases.¹⁹

2 Scintimammography. This involves the use of technetium-labelled sestamibi and, used as an adjunct to mammography, is comparable to MRM in both sensitivity and specificity in the demonstration of both palpable and impalpable tumours.¹⁸

Ultrasound

Ultrasound of the breast has increased in recent years, owing to advances in ultrasound technology. Ultrasound is a useful adjunct but is not a standalone method for imaging the breast. It is, however, used more extensively than MRI, computed tomography (CT) and radionuclide imaging (RNI). As breast ultrasound is frequently used in conjunction with mammography, more detail on this imaging modality is included following descriptions of mammography technique.

Digital breast tomosynthesis

Some newer digital mammography sets have this function. The woman is positioned as for a normal mammogram, but with a little less compression. The tube then moves over the breast in an arc, taking a series of low-dose images as it moves. Once these images have been reconstructed (a matter of seconds) a three-dimensional image is produced which is displayed as slices throughout the breast, much like a CT scan. This is particularly useful for dense breasts as it eliminates the problem of overlapping tissue. The use of tomosynthesis as part of a breast screening programme has been trialled in the US and results so far have demonstrated that, when performed as an adjunct to digital mammography, there is a 30–40% reduction in women being recalled for assessment.^20,²¹ When tomosynthesis is performed without digital mammography the recall rate is reduced by 10%.^20,²¹ Research is currently under way at King’s College Hospital in London to look into the potential of using tomosynthesis within the NHS breast screening programme.²²

Mammography technique

Equipment

The purchase, commissioning and quality control of suitable equipment are essential for the provision of a quality mammography service.²³ Equipment must be acceptable to both the operator and the client: it must be light and easy for the operator to use, and there must be no sharp edges in the sections of the unit that come into contact with the client. In addition, handles are necessary to help the client maintain the correct arm position for the oblique projection and for support, if necessary.

The machine consists simply of an X-ray tube connected to a breast support which houses the imaging detector on a C-shaped arm, with a moveable compression paddle between the two (Fig. 26.1).