Canadian Cancer Society logo

Breast cancer

You are here: 

Lobular carcinoma in situ (LCIS)

Lobular carcinoma in situ (LCIS) is not really a precancerous condition or a true breast cancer. LCIS is a marker that a woman is at an increased risk of developing an invasive ductal or lobular breast cancer in the future.

In LCIS, abnormal cells build up in the lobules of the breast, but they do not spread outside the lobules into nearby breast tissue. LCIS often occurs in many different parts of the breast and is more likely to occur in both breasts.

LCIS is not usually found on mammography or during clinical breast exam (CBE) (CBE). It is most often found after a biopsybiopsyThe removal of cells or tissues for examination under a microscope. for another reason, such as a suspicious breast lump or an abnormal mammogram.

While LCIS increases the risk, many women with LCIS do not develop invasive breast cancer. However, it is not yet known how to identify which women will eventually develop invasive breast cancer, and those who will not. Women with LCIS who also have other risk factors for breast cancer, such as a family history or BRCA gene mutations, may be at a greater risk for developing invasive breast cancer than women with LCIS who do not have other risk factors.

Because of this increased risk, early detection and screening for breast cancer are very important for women with LCIS. Women diagnosed with LCIS should talk to their doctor about a personal plan of follow-up and testing. A personal plan of testing may include:

  • more frequent mammography
  • frequent clinical breast exams

Women with LCIS may want to talk with their doctor about a personal plan of risk reduction strategies for breast cancer, which may include:

  • chemoprevention with tamoxifen (Nolvadex, Tamofen)
    • Tamoxifen has been shown to reduce the risk of developing breast cancer in women with LCIS.
  • prophylactic mastectomy
    • Removal of both breasts is usually reserved for women with LCIS who have other risk factors for breast cancer, which greatly increases their risk of developing the disease.


Researcher Dr Michael Taylor Dr Michael Taylor is revealing genetic changes in childhood brain cancer.

Learn more

Facing the financial burden of cancer

Illustration of coins

The Canadian Cancer Society provides helpful information about government income programs, financial resources and other resources available to families struggling to make sense of the personal financial burden they face.

Learn more