While it is quoted that screening mammography alone, has demonstrated a reduction in breast cancer mortality in the target population, the clinician should not be deterred from the addition of breast examination and breast ultrasound, when managing women referred to them with dense breasts.

What’s happening in the community

Where relevant, asymptomatic women with dense breasts who undergo a free BreastScreenWA mammogram, may be given a letter telling them they have dense breasts and to see their GP for further management. The GP receives a similar letter of notification.

Every two years BreastScreenWA contacts the target population of women, 50 – 74 years, inviting them to attend for a mammogram. Asymptomatic women from 40 – 49 years and 75 years and over, can also attend two yearly of their own volition. Women under 40 years cannot obtain a mammogram through BreastScreenWA.

Anatomical understanding

The breast is a modified sweat gland that sits between skin (including the subcutaneous fat) and the chest wall muscle. The post-pubertal non-lactating breast is glandular tissue with multiple breast ducts that open together at the nipple summit. At the peripheral margins of the ducts are inactive breast lobules (greatly expanded in the lactating breast). The filling tissue between the ducts and lobules is fibrotic tissue and some yellow fat.

The pubertal breast is all dense glandular tissue. The breast usually remains dense during regular menstruration and throughout the reproductive years. Pregnancy, breast feeding, obesity and hormonal fluctuations from around 40 years, tend to reduce the tissue density. Perimenopausal and menopausal women who are slim, nulliparous, taking HRT or have a strong family history of breast cancer are more prone to ongoing dense breast tissue.

Clinical significance

Very dense glandular breast tissue looks and feels like cooked squid at operation, and is the white tissue seen on mammogram.

Abnormal lumps and calcification, benign or malignant, are also white on mammogram. Hence if the breast is very dense, lumps and some abnormal calcification can be hidden in the solid white glandular tissue, during clinical examination and on mammogram.

How the films are reported

The ‘dense breast’ letter issued by BreastScreenWA usually refers to breast tissue density ³ 50%.

In non-BreastScreenWA mammogram reports, the radiologist may convey breast tissue density by including descriptive information; such as mixed density tissue, or by using a complex scoring system (e.g. Volpara), or giving percentage ranges (which I find the most reproducible and clinically functional – see Table).

Table: Working Guide on Breast Tissue Density in Women 40 Years and Over –  Dr Corinne Jones

What should we do about it?

All women of all ages should be encouraged to regularly check their own breasts. One to two yearly breast examination with their GP can be invaluable. The peripheries and edges of the breast should always have a detailed examination. Lumps in these locations can be missed as they ‘slip out’ of the mammogram plate as the breast is compressed.

Any breast abnormality in any woman or girl, should be followed by a bilateral breast ultrasound if < 35 – 40 years, and bilateral mammogram and breast ultrasound if > 35 – 40 years, with a request for reporting by an experienced breast radiologist.Breast MRI has limited use in the private sector because only women with PIP implants or <50 years with a very strong family history of breast cancer qualify for a Medicare rebate. The majority of lesions in the breast can be detected with good clinical examination, mammogram and breast ultrasound.

Only mammogram can detect fine, potentially malignant calcification.

Breast ultrasound can look at white glandular tissue and convey the nature of any rounded opacities seen on mammogram: benign simple cysts, complex cysts, solid lesions that are benign, indeterminate or malignant. The only way to define a solid or complex lesion is by tissue biopsy, usually a core biopsy or FNA if mostly a cystic mass.

Outside of BreastScreen WA there is no Medicare rebate for mammography in asymptomatic women. However it is still possible to obtain a Medicare rebate for the asymptomatic, screening breast ultrasound.

Hence the GP can provide a valuable service in continuing the management of women who present with dense breasts.

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