Invasive Ductal Carcinoma

April 10, 2025

This page was reviewed under our medical and editorial policy by Susan Yost, Ph.D., staff scientist, Department of Medical Oncology & Therapeutics Research, City of Hope^® Cancer Center Duarte

Invasive ductal carcinoma (IDC) is a type of breast cancer that forms in the milk ducts and has spread into other breast tissue.

IDC accounts for about 80% of breast cancer cases in women and men, making it the most common type of breast cancer. IDC is also sometimes called infiltrating ductal carcinoma.

What Is Invasive Ductal Carcinoma?

IDC is breast cancer that starts in the lining of the ducts that carry milk from the lobules to the nipple and then spreads out through the milk duct walls and into surrounding breast tissue. Without detection and treatment, the cancer cells may also spread (metastasize) to distant parts of the body through the lymph nodes (lymphatic system) and the blood.

Is It an Aggressive Cancer?

IDC is either slow-growing or aggressive, depending on the cancer grade. The grade of the cancer refers to how abnormal the cancer cells look compared to healthy cells — the more altered the cells, the more likely they are to grow quickly and spread. A doctor trained to diagnose diseases that begin in the cells and tissues (called a pathologist) examines a breast tissue sample under the microscope to determine the IDC grade.

If IDC is listed as Grade 3 cancer on the pathology report given to doctors and patients, it is considered an aggressive cancer. This means cancer cells have abnormal features that may cause them to grow faster, and they will likely spread into surrounding tissues and structures more quickly than lower-grade cancers.

IDC Versus. DCIS

Ductal carcinoma in situ (DCIS) is not considered invasive breast cancer. Instead, it is preinvasive or noninvasive, meaning it has not spread out from the milk duct lining where it formed. It is the earliest stage of breast cancer, known as Stage 0 breast cancer. This is important because doctors make treatment recommendations based in part on the cancer’s stage. It may become IDC in the future.

IDC, on the other hand, is considered invasive breast cancer because it has spread out or “invaded” the milk duct walls and surrounding breast tissue and sometimes the area lymph nodes and distant body parts.

Patients diagnosed with IDC will be told that the cancer is at one of five stages (Stages 1 to 4 or recurrent breast cancer). The stage is a measure of how far the disease has advanced (grown and spread). Patients will also be given certain treatment recommendations based on the breast cancer’s stage at diagnosis.

What Causes Invasive Ductal Carcinoma?

The causes of breast cancer, including IDC, are not fully known, but several risk factors increase a person’s risk for developing the disease. These include lifestyle factors that a person may be able to control and other factors that are out of one’s control. Having one or more of these risk factors does not mean the person will certainly develop the disease.

Lifestyle factors that may increase IDC risk include:

• A sedentary lifestyle (lack of exercise)
• Being obese or overweight
• Taking hormone-based birth control (contraceptives)
• Drinking alcohol
• Not breastfeeding
• Having never been pregnant
• Giving birth for the first time after age 30
• Taking menopausal hormone therapy (estrogen, progesterone or both)

Genetic and other risk factors for developing the disease may include:

• Being female
• Aging
• Race — being white (greatest risk) and Black (slightly less risk)
• A family history of breast cancer
• Having had breast cancer previously
• Early menstruation (before age 12)
• Late menopause (after age 55)
• Certain gene mutations passed down from a parent (inherited genes), most commonly in the BRCA1 and BRCA2 genes, and also in other genes like PALB2 and ATM
• Certain noncancerous (benign) conditions marked by lesions (damaged or abnormal tissue)
• Having radiation therapy to the chest
• Having dense breasts (higher amounts of glandular and fibrous tissue as compared to fatty tissue)
• Being taller
• Diethylstilbestrol (DES) exposure (an estrogen-like chemical)

Some potential factors are still being studied to determine if they affect breast cancer risk. These include tobacco smoke, eating a high-fat diet, working the night shift and estrogen-like environmental chemicals.

The more risk factors a person has for developing breast cancer, the greater the odds of developing the disease. Talking with a doctor about risk status helps patients understand their optimal breast cancer screening schedule.

Invasive Ductal Carcinoma Symptoms

When IDC is in its early stages, there are often no symptoms of the disease. Mammogram imaging tests are used to help detect cancer.

Symptoms may or may not appear as the cancer progresses. If they do, they might include:

• A lump in the breast or near the armpit
• Breast or lymph node swelling
• Breast pain
• Discharge from the nipple (that is not breast milk)
• Red, flaking, scaly or thickened breast or nipple skin
• An inverted nipple (turned inward)

Common symptoms of breast cancer in men may include:

• Breast tissue swelling
• A lump in the breast tissue, especially near the nipple
• One breast is larger than the other
• Nipple discharge
• Redness, puckering or scaling of the nipple or surrounding skin (breast cancer rash)

Sometimes if the disease progresses to more advanced stages, patients may experience additional symptoms, including:

• Bone pain
• Weight loss
• Lymph node swelling under the arm
• Shortness of breath

Diagnosing Invasive Ductal Carcinoma

When a screening mammogram finds tissue abnormalities that may be breast cancer or if a woman has symptoms of the disease, a diagnostic mammogram is performed, which typically involves taking additional views of the breast tissue.

If breast cancer is suspected after the diagnostic mammogram, a breast biopsy is performed to diagnose the disease. The doctor removes one or more tissue samples from the breast and sometimes from the lymph nodes. A pathologist then examines the tissue in the laboratory under a microscope to look for certain cell changes that may indicate IDC is present.

The doctor may also perform a physical examination of the breast and lymph nodes and review the patient’s medical history.

Additional imaging tests used to diagnose IDC may include:

• Breast ultrasound imaging that uses sound waves to take pictures of the breast tissue
• Magnetic resonance imaging (breast MRI) scans that use computers and magnets to produce detailed images
• Computed tomography (CT) scans that use a computer and X-rays to produce 3D images in order to see if cancer has spread beyond the breast
• Positron emission tomography (PET) scans that use radioactive glucose (since cancer cells tend to absorb glucose more than normal cells) and a scanner to check for cancer spread beyond the breast
• Bone scans that use a radioactive substance that pools in damaged parts of the bones, and a scanner to check for cancer that has spread to the bones

Newer imaging tests may also be used as part of the IDC diagnostic process. In addition, the doctor runs tests to understand certain details about the cancer in order to create a targeted treatment plan. These include hormone receptor tests to discover if the cancer cells have estrogen or progesterone receptors and biomarker tests to see if certain genes, gene changes or proteins like HER2 are present in the cancer cells.

Invasive Ductal Carcinoma Stages

People diagnosed with IDC are given a stage of the disease, which is the amount of cancer in the body. There are four main stages of IDC, with Stage 3 further divided into substages.

Stage 1: A small breast tumor is found that may or may not have spread to area lymph nodes.

Stage 2: Either a tumor that is about three-quarters of an inch to about 2 inches in size is found, along with small amounts of cancer in a few lymph nodes or a tumor larger than 2 inches is found with no cancer in the lymph nodes. The third possibility for this stage is that no tumor is found in the breast, but cancer is found in axillary (armpit) or breastbone-area lymph nodes.

Stage 3a: Either a tumor that is larger than 2 inches is found, along with cancer in at least three axillary or breastbone-area lymph nodes, or the cancer has spread into five to nine nearby lymph nodes but not beyond.

Stage 3b: The tumor has spread into the chest wall (fat, muscles, bones and tissues) or breast skin, and sometimes into the axillary lymph nodes, but not to other parts of the body.

Stage 3c: The cancer has spread to at least 10 axillary lymph nodes and sometimes into the breast wall or skin, but not to distant body parts.

Stage 4: The cancer has spread to distant sites in the body, such as the bones, lungs or brain.

To figure out each patient’s IDC stage, the care team looks at a number of different cancer cell and tumor features, including:

• Cell growth rate
• The size and extent of the tumor (marked by the letter T)
• The number of lymph nodes the cancer has spread into, if any (marked by the letter N)
• If the cancer has metastasized (spread) to distant sites in the body (marked by the letter M)
• If a protein called HER2 is present in high amounts (HER2 status)
• If estrogen or progesterone receptors (or both) are present on the cells (hormone receptor [HR]+/-)
• How close in appearance to normal cells the cancer cells look (cancer grade)

In addition, the chance of the cancer recurring may or may not be factored into the cancer staging criteria.

The system commonly used to measure several of the features above (tumor size [T], lymph node involvement [N] and spread [M] of the cancer) is called the TNM system.

Invasive Ductal Carcinoma Grades

Patients diagnosed with IDC receive a grade of cancer, along with a stage. The grade is part of what is used to determine the stage, and it measures how close to normal cells cancer cells look.

The Nottingham Grading System is used to grade cancer cells. It looks at three cell features to determine the grade:

• Degree of mitosis, which is cell reproduction rate (creating daughter cells from parent cells)
• Degree of nuclear pleomorphism, which is the degree of variation in cell size and shape
• Degree of tubular formation, which is how many of the cancer cells form into tube-like structures

Each of these features is measured and their scores are combined to assign a final grade of 1, 2 or 3.

Grade 1

Grade 1 IDC cells score 3 to 5 on their features. The cells look similar to normal cells and the cancer is slow-growing. This grade is sometimes called well-differentiated.

Grade 2

Grade 2 IDC cells score 6 or 7 on their features. It is also referred to as moderately differentiated. The cancer cells are growing a bit more quickly than normal cells and have a higher chance of spreading than Grade 1 IDC cells.

Grade 3

Grade 3 IDC cells score 8 or 9 on their overall features. It is also referred to as poorly differentiated. Cancer cells are growing quickly and look very different from normal, healthy cells.

Invasive Ductal Carcinoma Treatment

Doctors often recommend a combination of therapies and surgery to treat invasive ductal carcinoma. The types of treatments depend on a variety of factors, including the cancer’s stage, grade and subtype. The presence (or absence) of estrogen or progesterone receptors or certain genetic mutations or proteins in the cancer cells also influence the breast cancer treatment plan recommendations given to each patient. In this way, treatment plans are highly personalized to each patient.

For IDC, the care team may recommend those treatments listed below.

Surgery: Lumpectomy (partial breast removal) or mastectomy (entire breast removal) surgery may be performed. Most patients have one of these two types of surgeries to treat IDC.

Radiation therapy for breast cancer: This therapy uses high-energy particles to destroy cancer cells, and is often used after lumpectomy and sometimes after mastectomy surgery.

Systemic treatments: Chemotherapy, targeted drug therapy, hormone therapy and immunotherapy for breast cancer use drugs to help destroy or target parts of cancer cells in ways that slow their growth and spread.

What Is the Survival Rate of Invasive Ductal Carcinoma?

Experts tend to report survival rates for breast cancer by combining IDC, invasive lobular carcinoma (ILC) and other types as an overall rate. For women who receive treatment for all types of invasive breast cancer, in its early stages, the five-year relative survival rate was nearly 100% (99.6%) between 2014 and 2020, according to the National Cancer Institute SEER Program.

That five-year relative survival estimate is lower when the cancer has spread farther in the body. For instance:

• When it has spread to nearby lymph nodes, it is 86.7%
• When it has spread to distant parts of the body, it is 31.9%

In a 2022 study in the Journal of the National Cancer Institute, researchers studied the outcome of more than 32,000 U.S. patients with breast cancer to look at the differences between ILC and IDC. They found that:

• The estimated 10-year overall survival in patients with IDC is 73%
• The estimated 10-year overall survival in patients with estrogen-positive IDC is 77%

According to the American Cancer Society, for men, the five-year relative survival rate for invasive breast cancer (IDC and other breast cancer types combined) is:

• 95% when it is still in the breast tissue
• 84% when it has spread to area lymph nodes
• 20% when it has spread to distant parts of the body

Research to improve breast cancer treatments is ongoing, and newer therapies are being advanced to help improve early detection and patients’ chances of recovery.

The compassionate members of the City of Hope^® Breast Cancer Program are instrumental in guiding advances in IDC diagnostic testing and treatments to help elevate the treatment success of every patient in their care.