A carcinoma is any cancer that originates in the tissues covering or lining internal organs. In situ literally means that the cells are located in their original place. The most common form of breast cancer that is non-invasive, ductal carcinoma in situ (DCIS), originates in the milk ducts of the breast. DCIS is considered non-invasive because it remains in its place of origin and does not spread into the normal breast tissue that surrounds the affected milk ducts. DCIS is a stage 0 cancer and, as far as cancers go, it is the best diagnosis to receive relative to its alternatives. DCIS is non-life-threatening; however, having DCIS now increases your risk of invasive cancer developing at some point down the line. For a person who has or has had DCIS, the risk for recurrence or the development of a new, invasive cancer is greater than that of someone that has never had a form of breast cancer previously. Most of these recurrences occur within the 5 to 10-year span after the initial diagnosis.

The most common form of treatment for DCIS is a breast-conserving surgery called a lumpectomy, and women who have this procedure without subsequent radiation have a 25%-30% risk of a future recurrence. Women who choose to include radiation therapy in their treatment plan to reduce their recurrence risk to around 15%. Should the breast cancer recur after having received DCIS treatment, the chance of the recurrent cancer being invasive versus non-invasive is 50/50.

The American Cancer Society states that 1 out of every 5 new cases of breast cancer annually is DCIS, which accounts for about 60,000 cases of DCIS annually. There are two primary reasons this number is so large and is gradually increasing as time passes. These reasons are:

  • The risk of breast cancer increases with advanced age, and the lifespan of people in today’s society is much longer than it used to be.
  • The quality of cancer screening, such as mammograms, has improved with advancing technology, and more women are getting mammograms routinely as advised. This increased quantity and quality of screening enables more cancers to be spotted in their earlier stages.

DCIS is customarily asymptomatic, meaning no signs or symptoms are present to indicate something is wrong. A small number of women may develop a lump in the breast or a bloody discharge being expressed from the nipple. Indicators that you need to see your doctor for an exam include noticing an area of skin that is thickened underneath, puckered skin, skin that just doesn’t look right, or any other changes in your breasts that seem unusual. If something feels ‘off,’ it’s a pretty good indicator that a doctor should be consulted. The National Cancer Institute states that mammography identifies approximately 80% of DCIS cases.

If you are asking what causes DCIS, the answer is that “we’re still unsure.” It is known that DCIS occurs when the DNA of milk duct cells within the breast develop a genetic mutation. These mutations result in an abnormal appearance for the cells; however, it does not present the ability for the cells to escape from the milk duct. The variable that triggers these abnormal cells to grow and cause DCIS is still unknown to researchers. At this time, it is thought that a number of factors likely play a part. These include lifestyle, environment, and genetics received from your parents.

Some risk factors are believed to increase the risk of developing DCIS include:

  • A family history of breast cancer
  • A prior history of atypical hyperplasia or other benign breast diseases
  • Having genetic mutations that your greater risk of breast cancer, such as the BRCA1 and BRCA2 breast cancer genes
  • First pregnancy after age 30
  • Increasing age

It is important to remember that an absence of these risk factors does not negate your ability to still develop DCIS.

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