Lobular carcinoma in situ (LCIS)
- Medical Review: Regina Hampton, MD, FACS
Lobular carcinoma in situ (LCIS) is a non-cancerous change in the cells that line the inside of the breast lobules — the milk-producing glands in the breast.
While lobular carcinoma in situ cells have abnormal changes, they are not actually breast cancer. The cells stay confined (“in situ”) within the lobule walls.
LCIS is rare. It’s found in only about 2-2.5% of breast biopsies.
Since LCIS isn’t cancer, some doctors prefer the term lobular neoplasia (“neoplasia” means a new, abnormal growth of cells).
According to the American Cancer Society, the average lifetime risk of breast cancer is 13%. But for people with LCIS, the risk can be as high as 25-30%. The cancer can happen in either breast. It doesn’t always grow near the location where LCIS was originally found.
Researchers aren’t yet sure whether LCIS can actually turn into cancer, or if it is simply a marker for increased risk.
On this page, you can learn about how LCIS is diagnosed and treated, and what it means for reducing your risk of a future breast cancer.
How LCIS is diagnosed
Usually, LCIS doesn’t form a distinct lump or mass that can be felt during an exam or seen on a mammogram. It may not have the small calcium deposits (microcalcifications) that help some breast cancers show up on mammograms. That’s why lobular carcinoma in situ is often diagnosed after you have a biopsy for another reason, such as checking on an unusual change in breast tissue.
Still, LCIS can sometimes form a mass and/or have microcalcifications. Imaging tests such as mammogram, ultrasound, or breast MRI would show the abnormal area that requires further testing.
For most people, LCIS is confirmed after a needle biopsy, which removes tiny tissue samples from the area of concern. In some cases, your doctor may then recommend a surgical biopsy, also called an excisional biopsy, which removes a larger amount of the abnormal tissue, to confirm the diagnosis.
Doctors will also check the tissue sample for:
- Ductal carcinoma in situ (DCIS), which is non-invasive breast cancer in the breast ducts
- Invasive breast cancer, including invasive ductal carcinoma or invasive lobular carcinoma
In some cases, cancer cells are found close to the area of LCIS.
Types of lobular carcinoma in situ
There are three main types of LCIS:
- Classic LCIS: The cells in the breast lobules are small and all about the same size.
- Pleomorphic LCIS: The cells are larger and have a more abnormal appearance.
- Florid LCIS: The cells in the lobules have grouped together to form a mass. There’s often an area of dead cells in the middle. This is called central necrosis.
Classic LCIS is least likely to form a mass that shows up on a mammogram. Pleomorphic and florid LCIS types are more likely to have features that help them show up on a mammogram. They’re considered to be more advanced and faster-growing than classic LCIS, and they may have a higher risk of developing into cancer.
Treating LCIS
Treatment for lobular carcinoma in situ can vary depending on what type is found: classic, pleomorphic, or florid.
Treating classic LCIS
If a biopsy shows classic LCIS is present, you might not need any further treatment.
Your doctor will recommend a high-risk follow-up program with increased screening and breast exams. Screening will include mammograms and possibly other breast imaging (such as ultrasound). In some cases, risk-lowering medicine, such as tamoxifen, may be recommended.
If you had a needle biopsy with only a small sample (or samples) of tissue removed, your doctor may recommend a surgical (excisional) biopsy to remove the entire abnormal area.
An excisional biopsy is an operation that requires anesthesia. It does not require a hospital stay. Generally, an excisional biopsy for LCIS is needed only if there are concerns about the cells’ appearance. Your doctor may want to rule out the presence of other abnormal cells, such as cancer.
Treating pleomorphic and florid LCIS
For pleomorphic and florid LCIS, your doctor likely will recommend an excisional biopsy to remove the entire area. They also may recommend lumpectomy to take out the LCIS and a margin of healthy, normal tissue around it. This is called a clean margin.
With these types of LCIS, it’s important for your surgeon to remove clean margins when the abnormal tissue is removed. This means that the edges of the tissue don’t contain any LCIS cells. Pleomorphic and florid LCIS grow faster than classic LCIS and have a more abnormal appearance. They are not cancer, but they appear to have a higher risk of developing into invasive cancer than classic LCIS.
Your care team will recommend increased breast exams and screening as part of a high-risk follow-up program. For some people, tamoxifen or other risk-lowering medicine may be recommended.
Risk of developing breast cancer after LCIS
The average risk of breast cancer is 13%. After a diagnosis of LCIS, the risk of breast cancer in either breast may be as high as 25-30%. The type of breast cancer may be DCIS, invasive lobular carcinoma, or invasive ductal carcinoma.
Still, while an LCIS diagnosis means that you need to be followed carefully, it’s not a guarantee that you will develop breast cancer. Some research suggests that about 2% of women with LCIS are diagnosed with breast cancer each year.
It’s important to know that Black women appear to be at higher risk of developing invasive breast cancer after LCIS than women from other ethnic backgrounds. This includes cancer in the same breast or the opposite breast.
People who are diagnosed with LCIS and DCIS at the same time have a higher risk of developing breast cancer in the future than people diagnosed with LCIS alone, in the same or opposite breast.
Follow-up care after LCIS
LCIS is not an immediate threat to your health. Although it’s often removed with an excisional biopsy or lumpectomy, LCIS alone does not require additional treatment.
It is important to know that removing LCIS does not lower the risk of breast cancer. Talk with your doctor about a follow-up plan to manage your risk.
Recommendations can include:
- Seeing your doctor every 6 to 12 months for a breast exam
- Having mammography screening every 6 to 12 months
- Having additional breast cancer screening tests, such as breast MRI, if you have other risk factors for breast cancer
- Learning about lifestyle changes you can make to lower your risk, such as increasing exercise and reducing alcohol
- Taking medicines, such as tamoxifen, to reduce breast cancer risk
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Reviewed and updated: January 15, 2026
Reviewed by: Regina Hampton, MD, FACS
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