The Basics of DCIS

Ductal carcinoma in situ, or DCIS, is the most common kind of non-invasive breast cancer. The number of cases worldwide isn't known, because most international cancer registries don't keep track of DCIS. But in the United States, according to the American Cancer Society, about 60,000 cases of DCIS are diagnosed each year. There are two main reasons this number is so large and has been increasing over time:

1. Women are living much longer lives. As we grow older, our risk of breast cancer increases.
2. More women are getting mammograms, and the quality of the mammograms has improved. With better screening, more cancers are being spotted early.

It's important to know all the basics, so you can discuss them with your doctor and understand your diagnosis, treatment, and follow-up. You'll want to know:

• what DCIS means
• who's at risk for it
• how DCIS is diagnosed
• how serious it is

What does DCIS mean?

The name "ductal carcinoma in situ" has three parts:

• "Ductal" means that the cancer started in the milk ducts.
• "Carcinoma" refers to any cancer that begins in the skin or other tissues (including breast tissue) that cover or line the internal organs.
• "In situ" is Latin for "in its original place." This means that the cancer is non-invasive: it hasn't spread into any normal surrounding breast tissue.

Who is at risk for DCIS?

Women at high risk for DCIS are similar to women at high risk for developing invasive cancers. The shared risk factors include:

• never having had a full-term pregnancy
• having a first full-term pregnancy after age 30
• menstrual periods starting early
• late menopause
• having a parent or sibling with breast cancer
• more than 5 years of hormone replacement therapy (HRT), particularly with the therapy that combines estrogen and progestin
• having a breast cancer gene abnormality (BRCA1 or BRCA2)

How is DCIS diagnosed?

DCIS generally has no physical signs or symptoms. A small number of women may have a lump in the breast or some discharge coming out of the nipple.

DCIS is usually found by mammography. As the old cancer cells die off and pile up, tiny specks of calcium (called "calcifications" or "microcalcifications") form within the broken-down cells. The mammogram will show the buildup of cancer cells inside the ducts as a cluster of these microcalcifications or as a shadow or lump.

If you do have a suspicious mammogram, your doctor will probably want you to have a breast biopsy. There are two ways to get a biopsy done with only a little bit of surgery. (More invasive biopsies are rarely needed for DCIS):

1. Fine needle aspiration biopsy: A very small, hollow needle is inserted into the breast. A sample of cells are removed and examined under the microscope. An aspiration leaves no scars.
2. Core needle biopsy: A larger needle is inserted to remove several bigger samples of tissue from the area that looks suspicious. In order to get the core needle through the skin, the surgeon must make a tiny incision. This leaves a very tiny scar that is barely visible after a few weeks. The tissue samples are examined under a microscope. There is usually enough tissue to perform special tests, such as those for hormone receptors and HER2 status.

These tests are done to establish a diagnosis, not to remove the whole cancerous area. More surgery is needed to remove the whole cancer with clear margins.

How serious is DCIS?

DCIS is not life-threatening. It is non-invasive, and is considered the earliest form of cancer—Stage 0. Stage 0 breast cancer (sometimes called pre-cancer) is an uncontrolled growth of breast cells that is stuck inside the milk duct where it started. It has not yet figured out how to spread outside the duct or to other areas of the body.

Although this cancer stays inside the milk ducts, it raises the risk of getting an invasive cancer in the future. About 25% to 50% of women whose DCIS is treated by surgery ONLY (without radiation) eventually develop an invasive cancer. Most of those cancers (recurrences) happen within the first 5 to 10 years after a DCIS diagnosis.

But a new cancer may turn up 25 years later—or longer. This usually happens in the same area of the breast where the DCIS was. The new cancer can be either non-invasive (not life-threatening) or invasive (potentially serious). The main goal of treating DCIS is to reduce the risk of an invasive cancer later on.

In most cases, the treatment for DCIS is breast-conserving surgery (lumpectomy). The DCIS must be removed with clean margins (also called margins of resection). To substantially lower the risk of developing an invasive cancer, most doctors recommend additional treatment with radiation after surgery for DCIS.

Women with hormone-receptor-positive DCIS may choose to receive hormonal therapy after surgery to reduce the risk of recurrence and to lower the risk of getting a new cancer.