Disclaimer

We will often use “men” and “women” in this article to reflect the terms that have been historically used to gender people. But your gender identity may not align with your breast cancer risk. Your doctor can help you better understand how your specific circumstances will translate into breast cancer risk factors and symptoms.

With more than 280,000 people diagnosed in 2021, breast cancer is the most common cancer in the United States.

The most common form of breast cancer is invasive ductal carcinoma (IDC). It’s responsible for about 70 to 80 percent percent of all breast cancer diagnoses.

IDC, also known as infiltrating ductal carcinoma, gets its name because it begins in the milk-carrying ducts of the breast, and spreads to (or invades) surrounding breast tissue.

  • Invasive (or infiltrating) describes cancer that has spread beyond its site of origin. The opposite of this is “in situ.”
  • Ductal refers to where IDC starts — in the milk ducts. Most breast cancers begin in the ducts or lobules.
  • Carcinoma refers to cancer that begins in the skin cells or the tissues lining your internal organs.

So, IDC begins and spreads from the milk ducts. This is distinct from:

While IDC can affect people at any age, it’s most frequently diagnosed in women ages 55 to 74. This breast cancer can also affect men.

Healthy duct compared to DCIS and IDCShare on Pinterest
Invasive ductal carcinoma is cancer that starts in the milk ducts but spreads to surrounding tissue.

You can often detect IDC as a small lump in your breast. But other possible symptoms may be early signs of IDC, including:

Many people with IDC don’t experience any symptoms. They may not suspect anything until a doctor finds something on a mammogram. Regular screening mammograms can help ensure that potential cancers are spotted early.

Your doctor may perform several tests to diagnose IDC.

  • Physical exam: Your doctor will manually examine your breast for lumps or thickening.
  • Mammogram: A mammogram is an X-ray of your breast that can detect cancer.
  • Biopsy: Your doctor will send a sample of your breast tissue to a lab to be examined. A breast biopsy can help determine if a lump in your breast is cancerous or benign.
  • Ultrasound: A breast ultrasound uses sound waves to provide a detailed view of breast tissue and blood flow. It doesn’t use radiation and is safe for people who are pregnant.
  • MRI: Magnetic resonance imaging can detect small breast lesions. Doctors use breast MRIs to screen people who have a high risk of developing breast cancer.

Subtypes of invasive ductal carcinoma

IDC can appear in several different ways under a microscope. A biopsy will help your doctor understand which subtype of IDC you have.

About 70 percent of IDC cases are classified as no special type (NST). But when the cancer cells have special features, they may be classified as one of the following:

  • Medullary carcinoma: Another slow-growing cancer, these soft and fleshy tumors resemble the medulla of the brain. They account for less than 5 percent of all breast cancers.
  • Tubular carcinoma: These are slow-growing tumors with cancer cells that look like tubes. Tubular carcinomas account for less than 2 percent of all breast cancers.
  • Mucinous carcinoma: These low-grade tumors comprise cancer cells that live in mucin, a component of mucus. Mucinous carcinomas account for less than 2 percent of all breast cancers.
  • Papillary carcinoma: These are small cancer cells with finger-like projections. Papillary carcinomas are rare, accounting for less than 1 percent of all breast cancers.
  • Cribriform carcinoma: Another rare subtype, this cancer features a pattern of holes that resemble Swiss cheese. They account for less than 1 percent of all breast cancer.
  • Metaplastic carcinoma: This occurs when ductal cells change form to become different types of cells. Metaplastic carcinomas are usually a more aggressive form of cancer but account for less than 1 percent of all breast cancer.
  • Adenoid cystic carcinoma: These cancer cells look more like cancer cells found in the salivary glands than those usually found in ductal cells. They make up less than 1 percent of all breast cancers.

Your breast cancer may be a combination of some of the subtypes listed above.

HR and HER2 status

How your cancer looks under a microscope may not be as important as some of its other features. The pathology report from your biopsy will also reveal:

  • hormone receptor (HR) status: whether your cancer cells have receptors for the hormones estrogen and progesterone, which can fuel your cancer growth
  • human epidermal growth factor receptor 2 (HER2) status: whether your cancer cells are producing too much (HER2)

About 80 percent of breast cancers are ER-positive, meaning they test positive for estrogen receptor. Most ER-positive breast cancers are also PR-positive, meaning they also test positive for progesterone receptor. Only about 2 percent of cancers are PR-positive but ER-negative.

HER2 proteins exist in healthy breast cells, but too much HER2 can cause cancer to spread more quickly. About 14 percent of breast cancers are HER2-positive.

You may receive a diagnosis of triple-negative breast cancer (TNBC). This means that your cancer isn’t sensitive to estrogen or progesterone, and you don’t have an increased amount of HER2 protein. TNBC is usually more aggressive and tends to have a lower 5-year survival rate.

Talk with your medical team to learn more about what your HR and HER2 status mean for your treatment and outlook.

After diagnosis, the next step is determining the stage of your cancer. Staging is a measure of how large your cancer has grown and how much it has spread.

Many factors can influence staging. Doctors use what’s called TNM staging to assess three key factors:

  • Tumor: the size of the primary tumor
  • Nodes: involvement of nearby lymph nodes
  • Metastasis: how much the cancer has spread beyond its primary site

Combining information from those factors, doctors will usually assign IDC to one of four stages:

  • Stage 1: cancer that is localized to the breast with a tumor 2 centimeters (cm) or 3/4 inches (in) or less across
  • Stage 2: cancer that has spread to nearby lymph nodes in the underarms, or a breast tumor that is 2 to 5 cm (3/4 to 2 in) across
  • Stage 3: cancer that has spread extensively, but not beyond the breast, surrounding tissues, or lymph nodes
  • Stage 4: cancer that has spread to more distant sites in the body (metastasized)

DCIS is referred to as stage 0.

But other factors can also influence staging. They include:

  • tumor grade (how abnormal the cancer cells look and how quickly they’re likely to spread)
  • HR status
  • HER2 status

These factors can influence treatment and outlook.

Breast cancer, including IDC, is caused by changes to your DNA (mutations). Mutations in your breast cell DNA cause the cells to grow and divide too quickly. The abnormal cells clump together, forming the lump that you might feel.

But we don’t quite know what causes these DNA mutations. Genetic and environmental factors may both play a role.

Some factors increase your risk of developing breast cancer, including IDC. These include:

  • Age: Most people are diagnosed after the age of 50.
  • Genetics: Gene mutations such as BRCA1 and BRCA2 mutations account for 5 to 10 percent of all diagnoses
  • Family history of breast or ovarian cancer: If a first-degree relative (parent, sibling, or child) or multiple relatives on one side of your family have had breast or ovarian cancer, you’re at a higher risk of developing breast cancer.
  • Personal history of breast cancer: If you’ve had breast cancer before, you’re three to four times as likely to develop it again.
  • Radiation: If you had radiation to your chest to treat a different cancer before the age of 30, you’re at higher risk of developing breast cancer.
  • Reproductive history: Never carrying a child to full term or having your first child after the age of 30 increases your risk.
  • Hormone therapy: Long-term use of hormone therapies that include estrogen or progesterone could increase your risk.
  • Dense breasts: Women with dense breast tissue are twice as likely to develop cancer. It’s also harder to spot potential cancers on a mammogram.

Certain lifestyle factors also increase your risk. They include:

  • drinking alcohol
  • having obesity or being overweight
  • lack of physical activity
  • smoking
  • working at night or having high exposure to light at night

If you or someone you know has been diagnosed with IDC, rest assured that many different forms of treatment are available.

The treatments for IDC fall into two main types:

  • Local treatments for IDC target the cancerous tissue of the breast and the surrounding areas, such as the chest and lymph nodes. Options include:
    • surgery
    • radiation
  • Systemic treatments for IDC are applied throughout the body, targeting any cells that may have traveled and spread from the original tumor. Systemic treatments are effective at reducing the likelihood that the cancer will return after treatment. Options include:
    • chemotherapy
    • hormonal therapy
    • targeted therapy
    • immunotherapy

Surgery

Surgery removes the cancerous tumor and determines whether cancer has spread to the lymph nodes. Surgery is typically the doctor’s first response when dealing with IDC. Surgical options include:

  • lumpectomy, or removal of the tumor
  • mastectomy, or removal of the breast
  • lymph node dissection and removal

It takes about 2 weeks to recover from a lumpectomy and 4 weeks or more to recover from a mastectomy. Recovery times might be longer if you had your lymph nodes removed, had reconstruction done, or if there were complications.

Sometimes your doctor may recommend physical therapy to help with recovery from these procedures.

Systemic treatments, such as chemotherapy, may be given before surgery to shrink the tumor (neoadjuvant therapy), or after surgery to eliminate remaining cancer cells (adjuvant therapy).

Radiation

Radiation therapy directs powerful radiation beams at the breast, chest, armpit, or collarbone to kill any cells in or near the tumor’s location. Radiation therapy takes about 10 minutes to administer daily over the course of 5 to 8 weeks.

Some people treated with radiation may experience swelling or skin changes. Certain symptoms, such as fatigue, may take 6 to 12 weeks or longer to subside.

Different kinds of radiation therapies available for treating IDC include:

  • whole breast radiation, in which external beam radiation beams target the entire breast area
  • internal partial-breast radiation, in which radioactive materials are placed near the site of a lumpectomy
  • external partial-breast radiation, in which radiation beams directly target the original cancer site

Chemotherapy

Chemotherapy consists of anticancer medications you take in pill form or via IV. It may take up to 6 months or longer after treatment to recover from the many side effects, such as nerve damage, joint pain, and fatigue.

Many different chemotherapy drugs treat ICD, such as paclitaxel (Taxol) and doxorubicin (Adriamycin). Talk to your doctor about what’s right for you.

Hormonal therapy

Hormonal therapy treats cancer cells with receptors for estrogen or progesterone, or both. The presence of these hormones can encourage breast cancer cells to multiply.

Hormonal therapy removes or blocks these hormones to help prevent the cancer from growing. Hormonal therapy can have side effects that may include hot flashes and fatigue. How long it takes for side effects to subside after finishing treatment can vary based on the drug and the length of administration.

Some hormonal therapy drugs are taken regularly for 5 years or longer. Side effects can take several months to a year or more to wear off once treatment has stopped.

Types of hormonal therapy include:

Targeted therapies

Targeted therapies destroy breast cancer cells by interfering with specific proteins inside the cell that affect growth. Targeted therapies can take the form of:

  • monoclonal antibodies, which attach to specific proteins, like HER2, to stop them from growing (e.g., pertuzumab, trastuzumab)
  • antibody-drug conjugates, which combine monoclonal antibodies with chemotherapy drugs (e.g., Kadcyla, Enhertu)
  • kinase inhibitors, which block signals that tell a cell to grow or divide (e.g., lapatinib, neratinib)
  • PARP inhibitors, which help eliminate cells with mutated BRCA genes (e.g., olaparib, talazoparib)

Targeted therapies are less likely than chemotherapy to harm healthy cells, but they still have side effects. Pregnant women should not use targeted therapies.

Immunotherapy

Your immune system doesn’t usually detect cancer cells. Immunotherapy drugs help your immune system to spot cancer cells. These include:

  • checkpoint inhibitors, which block the systems that keep your immune system in check (e.g., dostarlimab, pembrolizumab)
  • monoclonal antibodies, which bind to cancer cells and allow them to be detected (e.g., pertuzumab, trastuzumab)
  • T-cell therapy, which allows your T cells to better detect cancer cells (still in clinical trials)

Your outlook for breast cancer depends on many factors, including

  • stage at diagnosis
  • age at diagnosis
  • HR and HER2 status

The stage of the cancer at diagnosis is most important to your outlook. The 5-year survival rate for breast cancers that are still localized is at least 91 percent for each hormonal subtype.

If cancer has spread to the lymph nodes or nearby tissue, the 5-year survival rate ranges between 65 and 90 percent depending on the subtype. For cancer that has metastasized, that range drops to 12 to 38 percent.

With so many variables, each person’s outlook is different. Chat with your medical team to learn more about your specific outlook based on factors that are unique to you.

Nothing can outright prevent you from developing IDC, but there are certain factors that can lower your risk:

  • maintaining a healthy weight
  • staying physically active
  • avoiding alcohol, or limiting yourself to no more than 1 drink per day
  • quitting smoking
  • breastfeeding for several months after childbirth

Chemoprevention

If your risk of getting IDC is high, your doctor may prescribe drugs that can help lower your risk. This is called chemoprevention. Drugs used for chemoprevention include:

But these drugs may have significant side effects. You and your doctor will need to weigh the risk of side effects against your risk of breast cancer.

Invasive ductal carcinoma is the most common type of breast cancer. There are local treatments that target specific parts of the body and systemic therapies that affect the whole body or multiple organ systems.

More than one type of treatment may be needed to effectively treat breast cancer. Talk to your doctor about the kind of treatment that is right for you.