Lobular Carcinoma In Situ (LCIS): Understanding Your Pathology Report

by Jason Wasserman MD PhD FRCPC
July 3, 2026

Lobular carcinoma in situ (LCIS) is a non-cancerous change in the breast. Despite having the word “carcinoma” in its name, LCIS is not a type of cancer and does not spread to other parts of the body. Instead, it is a marker that a person has an increased risk of developing breast cancer in the future. Another name for this change is lobular neoplasia in situ. The abnormal cells grow within the lobules, the small glands that produce milk, and they lose a protein called e-cadherin, which links LCIS to the lobular family of breast changes.

The most important thing to understand about LCIS is that the increased risk applies to both breasts, not only the breast where LCIS was found. The two types of breast cancer that may develop later are invasive ductal carcinoma and invasive lobular carcinoma. Most people with LCIS never develop breast cancer, but the finding is a reason for closer follow-up. This article will help you understand the findings in your pathology report, what each term means, and why it matters for your care.

What causes lobular carcinoma in situ?

Lobular carcinoma in situ develops when cells lining the breast lobules lose a protein called e-cadherin, which normally helps cells stick together. This loss is usually caused by a change in the gene CDH1 in breast cells themselves and is not inherited. Because the cells no longer stick together, they grow as loose, single cells that fill and expand the lobules. Like most breast changes, LCIS is influenced by lifetime exposure to the hormone estrogen, which is why it is most often found in women before menopause. In rare cases, an inherited change in the CDH1 gene is passed down through a family; when this is suspected, referral to a genetic counselor may be considered.

What are the symptoms of lobular carcinoma in situ?

Lobular carcinoma in situ does not cause any symptoms. It cannot usually be felt as a lump and does not reliably show up on a mammogram. For this reason, LCIS is almost always found incidentally, meaning it is discovered when a breast biopsy or surgery is performed for another reason.

How is the diagnosis made?

The diagnosis of lobular carcinoma in situ is usually made after a small tissue sample is removed by core needle biopsy, often performed to investigate another imaging finding. LCIS is also commonly discovered in tissue removed during surgery for another breast condition, such as ductal carcinoma in situ or an invasive cancer. Under the microscope, a pathologist sees small, uniform cells that are not attached to one another filling and expanding the lobules.

To confirm the diagnosis, the pathologist may perform an immunohistochemical (IHC) test for e-cadherin. In LCIS, the cells lose e-cadherin, so the test is negative (little or no staining). This loss is the hallmark that separates lobular changes from ductal changes, in which e-cadherin is kept. When LCIS is found on a core needle biopsy, especially the florid or pleomorphic types described below, or when the biopsy result does not match the imaging, the surgeon may remove the area (an excision) to make sure there is no associated cancer nearby.

Types of lobular carcinoma in situ

Pathologists recognize three types of lobular carcinoma in situ, based on how the cells look under the microscope. All three are associated with an increased risk of breast cancer, but the level of concern differs.

Classic type — The most common type. The cells are small and uniform, spread throughout the tissue as single, loosely attached cells. Classic LCIS is usually managed with follow-up rather than surgery.
Florid type — The lobules are greatly expanded and packed with abnormal cells, sometimes with dead cells (necrosis) in the center. This type is more concerning than classic LCIS and is often treated more like ductal carcinoma in situ.
Pleomorphic type — The cells are larger and more abnormal-looking than in the classic type, with a nucleus that is larger and hyperchromatic (darker than normal). Pleomorphic LCIS carries the highest risk and, like florid LCIS, is often removed with clear margins.

Your report may also mention comedonecrosis, which describes a group of cells with dead (necrotic) cells at the center. Comedonecrosis is more likely to be seen in florid and pleomorphic LCIS and is associated with a higher risk of developing breast cancer.

Is lobular carcinoma in situ staged?

Lobular carcinoma in situ is not given a cancer stage. Because it is not a cancer and does not spread, it does not receive a tumor (T), node (N), or metastasis (M) stage. In the past, classic LCIS was included in the “Tis” (in situ) category, but the American Joint Committee on Cancer removed it from the staging system in its 8th edition, reflecting the understanding that LCIS is a risk marker rather than a cancer. If an invasive cancer or ductal carcinoma in situ is found alongside LCIS, that cancer, not the LCIS, determines the stage.

What is the risk of developing breast cancer?

Lobular carcinoma in situ is best thought of as a risk marker. Having LCIS raises the chance of developing breast cancer in either breast to roughly 7 to 10 times that of the general population, which works out to about 1 to 2% per year and adds up over a lifetime. Even so, most people with LCIS never develop breast cancer. Several features influence the level of risk:

Type — Classic LCIS carries a lower risk than florid or pleomorphic LCIS.
Comedonecrosis — Its presence is associated with a higher risk.
Extent — More widespread LCIS may carry a somewhat higher risk than a small focus.
Personal and family history — A strong family history of breast cancer adds to the overall risk.

Importantly, the increased risk applies equally to both breasts, which is why follow-up looks at the entire breast tissue on both sides rather than just the area where LCIS was found.

What happens after this diagnosis?

Because lobular carcinoma in situ is a risk marker rather than a cancer, the goal after diagnosis is to lower the future risk of breast cancer and to watch closely so that any cancer that does develop is found early. Care is often coordinated with a breast surgeon and, when appropriate, a medical oncologist. The pathology findings guide which options the team discusses, rather than dictating a single path.

Surveillance — Regular clinical breast examinations and imaging, sometimes including breast MRI in addition to mammography, help find any future cancer early.
Risk-reducing medication — Medications that block or lower estrogen, such as tamoxifen, raloxifene, or an aromatase inhibitor, can substantially lower the risk of developing breast cancer and may be discussed for classic LCIS.
Surgery — For florid or pleomorphic LCIS, or when a core needle biopsy result does not match the imaging, the area may be removed with clear margins to make sure there is no nearby cancer. Preventive (risk-reducing) surgery is occasionally considered for people at very high overall risk, usually because of additional factors such as a strong family history.
Genetic counseling — Considered when there is a strong family history or a suspected inherited CDH1 change.

Questions to ask your doctor

Is my lobular carcinoma in situ the classic, florid, or pleomorphic type?
Was comedonecrosis present?
Was the LCIS found on a needle biopsy, and do I need surgery to remove the area?
Was any invasive cancer or ductal carcinoma in situ found along with the LCIS?
How much does this finding increase my risk of developing breast cancer?
Does the increased risk apply to both breasts?
What surveillance schedule and imaging (including MRI) do you recommend?
Would a risk-reducing medication such as tamoxifen or an aromatase inhibitor be appropriate for me?
Should I be referred for genetic counseling based on my personal or family history?
What signs or symptoms should prompt me to contact you between visits?