Breast cancer screening with mammography

What it is

Screening for breast cancer is mammography. It is offered to women 40 to 74 years, an age band that varies by guideline, every 1 to 2 years. The pearl to hold is short: breast cancer means mammography, not ultrasound and not MRI.

A woman who comes with a lump is a separate matter from a woman who comes for screening. A breast mass is worked up by triple assessment: clinical history and examination, imaging, and histopathology or cytology.

How it is diagnosed

Which imaging is chosen depends on age, and this is the point most often confused with the screening age.

• Younger than 35 years: breast ultrasound.
• Older than 35 years: ultrasound plus mammogram.

The reason is the tissue itself. In young ages the breast is dense and has more glandular tissue, while in older ages fat replaces the glands, which is why mammogram is not very sensitive in young ages. Mammogram is 80% sensitive but lower in younger women, and it can still be done under 35 years if there is a high index of suspicion. Mammogram is contraindicated in lactating and pregnant women.

The mammogram features that matter are asymmetry, architecture distortion, opacification with spiculation or irregular margins, microcalcification that is usually irregular in size and shape, skin thickening and nipple inversion. MRI is kept for the post-treated breast, for concern about multifocality or multicentre disease in a young patient, and for BRCA1 and 2.

The result comes back as a BIRAD score. 0 is incomplete and needs follow-up imaging. 1 is negative and 2 is a definite benign finding; both go back to routine screening. 3 is probably benign, with a high probability of being benign above 98%, and takes a six-month short interval follow-up. 4 is a suspicious abnormality and biopsy should be considered. 5 is highly suspicious of malignancy, at or above 95%, and takes appropriate action. 6 is a known biopsy proven malignancy being imaged before definitive treatment.