Invasive Lobular Carcinoma

Medically Reviewed by Jennifer Robinson, MD on March 17, 2023
5 min read

Invasive lobular carcinoma (ILC) is breast cancer that begins in one of the glands that make milk, called lobules, and spreads to other parts of the breast. It’s the second most common form of breast cancer after invasive ductal carcinoma, which begins in a milk duct.

It’s different from lobular carcinoma in situ (LCIS). That’s another type of abnormal cell growth in the breast that stays inside the lobules.

ILC is more likely to be found in both breasts than other types of breast cancer. It can also spread to other areas of your body.

You might not notice symptoms at first. If you do, they can include:

  • Thickening or hardening in the breast (rather than a distinct lump)
  • An area of swelling or fullness
  • A change to the texture of skin on your breast or nipple, like dimples or an irritated, red, or scaly area
  • A nipple that turns inward
  • Pain in your breast or nipple
  • Unusual nipple discharge
  • A lump under your arm

Experts aren’t sure exactly what causes breast cancer. It happens when cells change and start to grow out of control.

Things that can make ILC more likely include:

Your doctor will start with a physical exam of your breasts and nearby lymph nodes. If they feel any problems like thickening, hardening, or swelling, you may have tests including:

  • Mammogram. ILC can be hard to spot on a mammogram, which makes X-ray pictures of your breast, because the cancer cells tend to grow in a line rather than in a mass.
  • Ultrasound. Sound waves create images of the inside of your breast. An ultrasound may be better at finding ILC than a mammogram.
  • Biopsy. If they find a suspicious area, your doctor will order a biopsy to check the cells. Most biopsies use a needle to take out a sample of cells from the breast. In some cases, the doctor will remove a larger sample or the entire tumor.
  • CT scan. This is a powerful X-ray that makes detailed pictures inside your body.
  • PET scan. Along with a CT scan, this test can help find cancer in lymph nodes and other areas.
  • MRI. This uses strong magnets and radio waves to make pictures of the breast and things inside your body.
  • Bone scan. A radioactive material called a tracer is injected into your arm. It shows up on pictures to tell your doctor whether cancer may have traveled to your bones.
  • The results of your exams will tell your doctor whether you have cancer and whether it’s spread so they can recommend the best treatment options.

Treatment for ILC involves one or more methods. Surgery and radiation therapy are local treatments, meaning they focus on the area of the cancer. Systemic treatments, like chemotherapy and hormone therapy, target any cancer cells that may have spread.


Most women with invasive lobular carcinoma have surgery. Depending on the size of your tumor and how much it’s spread, you may have one of two types:

  • Lumpectomy. Your doctor takes only the tumor and some of the tissue around it.
  • Mastectomy. They remove part or all of your breast, with or without nearby lymph nodes and muscle.

Your doctor may take samples from the lymph nodes in your armpits to check for cancer. They might also remove the lymph nodes. These procedures are called sentinel lymph node biopsy and axillary lymph node dissection.

Radiation therapy

High-energy radiation can destroy cancer cells that may be left behind after surgery. Your doctor may use a machine to deliver the energy from outside your body (external) or insert radioactive seeds or pellets into your body near where the cancer was removed (internal).


Chemotherapy, or “chemo,” is when your doctor uses one or more medicines to kill cancer cells. You may get them before surgery to shrink a tumor or afterward to destroy any remaining cells. They come in pills that you swallow and in liquid that goes directly into your bloodstream (intravenous, or IV). Drugs that can treat ILC include:

Hormone therapy

ILC cells often have receptors for the hormones estrogen and progesterone. Receptors are special proteins that help the hormones tell cells to grow and divide. Hormone therapy drugs for ILC lower the amount of estrogen in your body or keep it from telling cancer cells to grow. Common ones include:

A protein called HER2 can also tell cancer cells to grow. Other medicines target this protein or its receptors.

Treatment side effects

You may notice side effects during or after cancer treatment. For example, chemotherapy can cause:

Radiation may cause:

  • Breast swelling
  • Pain
  • Skin changes, redness, or bruising
  • Fatigue
  • Breast tissue changes
  • Problems breastfeeding
  • Nerve damage
  • Pain and swelling in your arm or chest (lymphedema)
  • Weakened ribs that fracture more easily
  • Fluid in your breast (seroma)

Before you start treatment, talk with your medical team about what to expect. Let them know if you notice any side effects. Some treatments may be available to help you feel better.

Cancer affects everyone differently. Your outlook may depend on things like how early you’re diagnosed and how well your body responds to treatment.

In general, about 90% of all women with breast cancer live at least 5 years after diagnosis. While there isn’t much information about specific types of breast cancer, these survival rates are tracked by stage at diagnosis or how far the cancer has spread:

  • Localized (cancer hasn’t spread outside the breast): 99% live at least 5 years.
  • Regional (cancer has spread to lymph nodes near the breast): 85% live at least 5 years.
  • Distant (cancer has spread farther in the body): 30% live at least 5 years.