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Ductal Carcinoma In Situ (Breast)
Health Guide
What is ductal carcinoma in situ?

The breast is made up of fat, fibrous tissue and glandular tissue. The glandular tissue comprises ducts and lobules/ milk glands. The ducts are the hollow tubes by which the milk produced in the lobules / milk glands is carried to the nipple. The ducts and lobules/milk glands are lined with cells. It is these cells which can become pre-cancerous and then have the ability to become cancerous.

The actual term ductal carcinoma in situ is confusing and alarming. Because the word carcinoma is used the natural assumption is that DCIS is invasive cancer. This is not correct. DCIS is a pre-malignant or pre-cancerous condition of the breast. It is not invasive cancer but it does have the potential to change to invasive cancer if left in the breast. The main difference betweeen invasive cancer and precancer is that invasive cancer has the ability to invade into blood or lymph vessels and spread through out the body. Precancer or DCIS is not able to do this as the cells are contained within the duct walls (see diagram).

DCIS is graded by the pathologist into either high, intermediate or low grade. It is thought that high grade DCIS definitely becomes invasive in the time frame of a few years while low grade DCIS probably becomes cancerous but over a longer time period - 10-20 years. The intermediate grade DCIS has activity lying between high and low grade. Looking at all grades of DCIS, across the board, 50% will become invasive within 3 years if left in the breast.

How is DCIS detected?

DCIS can be detected in three ways. Mammography would be the most common way that it is detected. On a mammogram DCIS presents as tiny white grains of calcium (microcalcifications ). No one is absolutely sure why the breast lays down microcalcifications. One theory is that with malignant/pre-malignant conditions there is an abnormal production and turn over or death of cells. With cell death, calcium is a by-product. Sometimes it can present as a lump or thickening in the breast. This is because the body recognises that DCIS as a potential enemy and tries to strangulate it with a fibrous bandage. Sometimes it is picked up incidentally when there is a surgical biopsy for a totally different reason.

What are the significance of microcalcifications seen on a mamogram ?
Sometimes on a mammogram tiny white grains of calcium or microcalcifications are seen. No one knows exactly why, in certain circumstances, the breast lays down calcium. Fortunately the majority of microcalcifications seen on mammogram are due to benign changes and often represents an ageing process. There are four main classifications of microcalcifications - malignant, pre-malignant, indeterminant and benign. The malignant and benign type microcalcifications have a characteristic pattern that is very easy to detect. Sometimes it is easy to distinguish the premalignant calcifications that are associated with DCIS but this is not always the case. When the calcification pattern is unclear they are called indeterminant. To determine the nature of these microcalcifications, there are two options available. The microcalcifications can be biopsied either surgically or by stereotactic core. The other option is to do a repeat mammogram in 6 months time. The absence of any change over this time interval would suggest that the calcifications are a result of a benign process. Because the process of precancerous cells turning invasive takes years reviewing the area through a 6 month mammogram is not felt to jeopardise the situation.
How is DCIS treated ?

DCIS is a modern disease. It did not 'exist' 20 years ago because it has only been through high quality, modern mammography that it has been possible to detect microcalcifications.

The main treatment of DCIS is surgical. By removing the area the potential of these cells becoming cancerous is eliminated. To ensure that all the precancerous cells are removed, there has to be an adequate margin of healthy tissue from the DCIS to the surgical margin.

The place of radiotherapy and tamoxifen in the treated of DCIS is not yet proven. There are world - wide trials looking at the treatment of DCIS. This data will not be available for some time. At St Marks Breast Centre we encourage participation of these trials as they will be the only way that we will be able to determine the correct treatment of DCIS. Our preference is for ensuring clear surgical margins and advising radiotherapy to the breast especially in the case of high or intermediate grade DCIS. Radiotherapy sterilises the rest of the breast tissue so that the process of normal cells becoming precancerous and precancerous cells becoming invasive is halted.

What is my outlook if I have had DCIS?

Your outlook is excellent. DCIS is a precancerous process and NOT invasive cancer. Invasive cancer has the ability to invade into blood or lymph vessels and then spread throughout the body. By removing the area surgically a woman is considered to have 98% survival at 10 years. This means that of 100 woman who have had DCIS, 98 will be alive at 10 years. In cancer terminology that is the closest description to "cure" that is used.

Because DCIS has been detected in one breast it does mean that there is a small, increased risk of developing a similar process in the same or other breast compared to a woman who has never had DCIS. An annual mammogram and 6 monthly clinical/breast ultrasound examination for the first 5 years following diagnosis is recommended for women who have been diagnosed with DCIS. For the subsequent years an annual mammogram and clinical examination is required.Link to St Marks Breast Centre Online

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