Invasive Lobular Breast Cancer (ILC)


Invasive lobular breast cancer (ILC), also known as infiltrating lobular carcinoma, is the second most common form of invasive breast cancer. It makes up 10 to 15 percent of breast cancer cases.

The condition begins when abnormal cells develop in the milk gland, known as lobules, in the breast. These cancer cells then spread to other parts of the body. Because of this, treatment of invasive lobular cancers requires surgery to remove the cancer in the breast, as well as some of the underarm lymph nodes to determine the cancer stage.


Early stages of ILC often have no symptoms. As the condition progresses, patients may notice the following symptoms:

  • Breast lump
  • Nipple discharge
  • Thickening of the breast skin
  • Rash or redness on the breast
  • Swelling in one breast
  • Dimpling of the nipple or breast skin
  • Rash on the nipple
  • The nipple turning inward
  • Lumps in the underarm
  • Unusual changes in breast or nipple appearance

Causes and Risk Factors

The cause of ILC is unknown. Patients with an inherited disorder known as hereditary diffuse gastric cancer syndrome are at an increased risk of developing certain cancers, including ILC.

Other risk factors include:

  • Age — risk increases with age
  • Gender — women have a higher risk than men
  • Diagnosis of lobular carcinoma in situ (LCIS)
  • Using combination estrogen-progestin hormone replacement therapy after menopause


ILC may be diagnosed during a mammogram. However, due to the nature of ILC tumors, they are often difficult to see on a mammogram. Other imaging tools such as magnetic resonance imaging (MRI) or ultrasound may be used to study the area of concern.

If the medical team sees evidence of ILC, a biopsy will be performed. During a biopsy, a sample of the abnormal tissue will be taken using a needle. The doctor may use stereotactic images, such as mammography or ultrasound, to guide the needle to the area of concern. A specialist, known as a pathologist, will examine the tissue sample under a microscope and determine if cancer is present.


Treatment of ILC will depend on the characteristics of the tumor present, including the type, size and spread of the tumor. Treatment will generally involve surgery to remove the abnormal cells as well as additional treatment such as radiation therapy or chemotherapy.

  • Surgery. Surgery to remove the affected tissue may include breast-sparing techniques or removing the entire breast. A lumpectomy, which removes the affected tissue while preserving as much of the natural breast tissue as possible, is the most conservative option and is generally paired with radiation therapy.
    For some patients, a mastectomy, a procedure that removes all of the breast tissue, may be the best course of treatment. There are different forms of mastectomy surgeries including nipple-sparing and skin-sparing options.
    Removing the lymph nodes in the underarms may also be needed. This can be done as either a sentinel lymph node biopsy or axillary lymph node dissection.
  • Radiation therapy. Radiation therapy may be paired with surgery. This method uses high-energy radiation to kill the cancer cells. The radiation may be directed from outside the body (external) or it may come from an implant placed inside the breast.
  • Chemotherapy. Chemotherapy may also be used as a second form of treatment in addition to surgery. This method uses drugs to kill the cancer cells. The drugs may be provided through a pill or through an IV.
  • Hormone therapy. Estrogen has been associated with breast cancer. For some patients, hormone therapy may be an option. This method of treatment blocks estrogen from reaching the breast tissue.

© 2000-2022 The StayWell Company, LLC. All rights reserved. This information is not intended as a substitute for professional medical care. Always follow your healthcare professional's instructions.
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