Invasive Ductal Carcinoma (IDC) & Ductal Carcinoma In Situ (DCIS)

Medically Reviewed by Sabrina Felson, MD on March 26, 2023
8 min read

Ductal carcinoma is a common type of breast cancer that starts in cells that line the milk ducts, which carry breast milk to the nipple.

There are two types:

  • Invasive ductal carcinoma (IDC)
  • Ductal carcinoma in situ (DCIS), also called intraductal carcinoma

The symptoms, diagnosis, and treatments for each are different.

Invasive ductal carcinoma (IDC) accounts for about 80% of all invasive breast cancers in women and 90% in men.

It begins in the cells of a milk duct, then it grows through the duct walls and into the surrounding breast tissue. It can also spread to other parts of your body.

Invasive Ductal Carcinoma symptoms include:

  • A lump in your breast
  • Thickened breast skin
  • Rash or redness on your breast
  • Swelling in your breast
  • New pain in your breast
  • Dimpling on your breast or the skin of your nipple
  • Nipple pain
  • Inverted nipple
  • Nipple discharge
  • Lumps under your arm
  • Changes to your breast or nipple that are different from the ones you have with your period

IDC is usually found as the result of an abnormal mammogram. To diagnose cancer, you’ll get a biopsy to collect cells for analysis. The doctor will remove a bit of tissue to look at under a microscope. They can make a diagnosis from the biopsy results.

If the biopsy confirms you have cancer, you’ll likely have more tests to see how large the tumor is and if it has spread:

  • CT scan. It's a powerful X-ray that makes detailed pictures inside your body.
  • PET scan. The doctor injects a radioactive substance called a tracer into your arm. It travels through your body and gets absorbed into the cancer cells. Together with a CT scan, this test can help find cancer in lymph nodes and other areas.
  • MRI. It uses strong magnets and radio waves to make pictures of the breast and other structures inside your body.
  • Bone scan. The doctor injects a tracer into your arm. They take pictures to find out if cancer has traveled to your bones.
  • Chest X-ray. It uses low doses of radiation to make pictures of the inside of your chest.

Results from these tests will show the stage of your cancer. Staging is the name for the process doctors use to figure out if and how far breast cancer has spread. Knowing the stage will help guide your treatment.

Doctors can use the results from your diagnostic testing to gather information about the tumor. They group it by a system known as TNM:

  • Tumor (T): How large is the primary tumor? Where is it?
  • Node (N): Has the tumor spread to your lymph nodes? Where? How much?
  • Metastasis (M): Has the cancer spread to other body parts? Which ones? How much?

To stage your cancer, your doctor combines the TNM results with the tumor grade (how your tumor cells and tissue look under a microscope and your hormone receptor status (if the cancer cells have proteins that respond to the hormones estrogen or progesterone and your HER2 status (whether your cancer is affected by the HER2 gene).

Stages include:

  • Stage 0: This is noninvasive cancer. It’s only in the ducts and hasn’t spread (Tis, N0, M0).
  • Stage IA: The tumor is small and invasive, but it hasn’t spread to your lymph nodes (T1, N0, M0).
  • Stage IB: Cancer has spread to the lymph nodes. It’s larger than 0.2 mm but less than 2 mm in size. There’s either no sign of a tumor in the breast or there is, but it’s 20 mm or smaller (T0 or T1, N1, M0).
  • Stage IIA: Any one of these:
    • There’s no sign of a tumor in the breast. The cancer has spread to between 1 and 3 underarm lymph nodes, but not to any distant body parts (T0, N1, M0).
    • The tumor is 20 mm or smaller and has spread to underarm lymph nodes (T1, N1, M0).
    • The tumor is between 20 mm and 50 mm but hasn’t spread to nearby nodes (T2, N0, M0).
  • Stage IIB: Either of these conditions:
    • The tumor is between 20 mm and 50 mm and has spread to one to three underarm lymph nodes (T2, N1, M0).
    • The tumor is larger than 50 mm but hasn’t spread to underarm lymph nodes (T3, N0, M0).
  • Stage IIIA: Either of these conditions:
    • Cancer of any size has spread to four to nine underarm lymph nodes or those under your chest wall. It hasn’t spread to other body parts (T0, T1, T2 or T3, N2, M0).
    • A tumor larger than 50 mm has spread to one to three nearby lymph nodes (T3, N1, M0).
  • Stage IIIB: The tumor:
    • Has spread to the chest wall
    • Has caused swelling or breast sores
    • Has been diagnosed as inflammatory breast cancer
    • May or may not have spread to up to nine lymph nodes under your arm or beneath the chest wall
    • Hasn’t spread to other body parts (T4; N0, N1 or N2; M0)
  • Stage IIIC: A tumor of any size that has spread to 10 or more nearby lymph nodes, breast lymph nodes, and/or lymph nodes under the collarbone. It hasn’t spread to other body parts (any T, N3, M0).
  • Stage IV (metastatic): The tumor can be any size and has spread to other organs, like your bones, lungs, brain, liver, distant lymph nodes, or chest wall (any T, any N, M1). Between 5% and 6% of the time, metastatic cancer is discovered upon first diagnosis. Your doctor may call this de novo metastatic breast cancer. More often, it’s found after a previous diagnosis of early breast cancer.
  • Recurrent: This is cancer that comes back after treatment. It can be local, regional, and/or distant. If your cancer returns, you’ll get another round of tests to learn about the extent of the recurrence. They’ll be similar to those at your original diagnosis.

Most women with IDC have surgery to remove the cancer. The treatment options are usually:

  • Lumpectomy: The surgeon only removes the tumor and a bit of the tissue around it to help make sure all the cancer cells have been removed. You might hear it called breast-conserving surgery
  • Mastectomy: The surgeon removes an entire breast.

Which one you get depends on the size of your tumor and how much it has spread throughout your breast and surrounding lymph nodes.

In addition to surgery, other treatments may include:

  • Radiation: This usually follows your surgery.
  • Hormone therapy: You’ll get it if your cancer is hormone receptor-positive (meaning estrogen helps it grow). These drugs block or lower the amount of estrogen in your body.
  • Chemotherapy: These medications target cancer cells throughout your body. Doctors may also use It before surgery to shrink tumors and after to kill any cancer cells left behind.
  • Targeted therapy: These medications block cancer cell growth. You might get them along with chemotherapy.

You might get one treatment or a combination.

Ductal Carcinoma in Situ (DCIS), also known as intraductal carcinoma, accounts for one of every five new breast cancer diagnoses. It's an uncontrolled growth of cells within the breast ducts. It’s noninvasive, meaning it hasn’t grown into the breast tissue outside of the ducts. The phrase "in situ" means "in its original place."

DCIS is the earliest stage at which breast cancer can be diagnosed. It's known as stage 0 breast cancer. The vast majority of women diagnosed with it can be cured.

Even though it’s noninvasive, it can lead to invasive cancer. It's important that women with the disease get treatment. Research shows that the risk of getting invasive cancer is low if you’ve been treated for DCIS. If it isn’t treated, 30% to 50% of women with DCIS will get invasive cancer. The invasive cancer usually develops in the same breast and in the same area as where the DCIS happened.

DCIS usually has no symptoms. Most of the time, it’s diagnosed by a mammogram.

About 80% of cases are found by mammograms. On the mammogram, it appears as a shadowy area.

If your mammogram suggests that you may have DCIS, your doctor should order a biopsy to analyze the cells and confirm the diagnosis. Biopsies for DCIS are typically done using needles to remove tissue samples from the breast.

If you have DCIS, your doctor may do more tests to gather information about your cancer. These tests may include an ultrasound or MRI. Based on the results of various tests, your doctor will be able to tell the size of your tumor and how much of your breast is affected by the cancer.

Your doctor will customize your treatment plan based on your test results and medical history. Among other things, your doctor will consider:

  • Tumor location
  • Tumor size
  • Aggressiveness of the cancer cells
  • Your family history of breast cancer
  • Results of tests for a gene mutation that would increase the risk of breast cancer

Most women with DCIS don't have the breast removed with a mastectomy. Instead, they have a lumpectomy.

Most common is a lumpectomy followed by radiation. The surgeon removes the cancer and a small area of healthy tissue around it. Lymph nodes under the arm don’t need to be removed as they are with other types of breast cancer.

After a lumpectomy, radiation cuts the chances that the cancer will come back. If cancer does return, it’s called recurrence.

Some women may opt to have a lumpectomy only. Discuss the risks of not having radiation with your doctor before deciding against it.

You and your doctors may decide that a mastectomy to remove the breast is the best course of treatment if you have any of the following:

  • A strong family history of breast cancer
  • A gene mutation that makes having breast cancer more likely
  • Very large areas of DCIS
  • DCIS lesions in multiple areas throughout your breast
  • Not being able to tolerate radiation therapy

You and your treatment team may also consider the use of hormone therapy if the cancer tests positive for hormone receptors. It can cut the chance of getting another breast cancer.