Each breast contains 15 to 20 lobes of glandular tissue, arranged like the petals of a daisy. The lobes are further divided into smaller lobules that produce milk for breastfeeding. Small tubes (ducts) conduct the milk to a reservoir that lies just beneath your nipple.
Ductal carcinoma in situ (DCIS) is the presence of abnormal cells inside a milk duct in the breast.
DCIS is considered the earliest form of breast cancer. DCIS is noninvasive, meaning it hasn't spread out of the milk duct and has a low risk of becoming invasive.
DCIS is usually found during a mammogram done as part of breast cancer screening or to investigate a breast lump.
While DCIS isn't an emergency, it does require an evaluation and a consideration of treatment options. Treatment may include breast-conserving surgery combined with radiation or surgery to remove all of the breast tissue. A clinical trial studying active monitoring as an alternative to surgery may be another option.
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DCIS doesn't typically have any signs or symptoms. However, DCIS can sometimes cause signs such as:
- A breast lump
- Bloody nipple discharge
DCIS is usually found on a mammogram and appears as small clusters of calcifications that have irregular shapes and sizes.
When to see a doctor
Make an appointment with your doctor if you notice a change in your breasts, such as a lump, an area of puckered or otherwise unusual skin, a thickened region under the skin, or nipple discharge.
Ask your doctor when you should consider breast cancer screening and how often it should be repeated. Most groups recommend considering routine breast cancer screening beginning in your 40s. Talk with your doctor about what's right for you.
It's not clear what causes DCIS. DCIS forms when genetic mutations occur in the DNA of breast duct cells. The genetic mutations cause the cells to appear abnormal, but the cells don't yet have the ability to break out of the breast duct.
Researchers don't know exactly what triggers the abnormal cell growth that leads to DCIS. Factors that may play a part include your lifestyle, your environment and genes passed to you from your parents.
Factors that may increase your risk of DCIS include:
- Increasing age
- Personal history of benign breast disease, such as atypical hyperplasia
- Family history of breast cancer
- Never having been pregnant
- Having your first baby after age 30
- Having your first period before age 12
- Beginning menopause after age 55
- Genetic mutations that increase the risk of breast cancer, such as those in the breast cancer genes BRCA1 and BRCA2