Lobular carcinoma in situ (LCIS)

LCIS is not a cancer. It is when the terminal duct lobular units of the breast fill with abnormal cells that all look very similar but have lost the ability to stick to each other. LCIS is also known as lobular neoplasia or in situ lobular neoplasia.

The breast is made up of a series of branching tubes (ducts) that start at the nipple and end in small glands called the terminal duct lobular units. The terminal duct lobular unit is responsible for making breast milk after pregnancy.

In LCIS the abnormal cells stay in the ducts and can’t spread into the surrounding breast tissue. This is different to invasive breast cancer where the abnormal cells have broken through the ducts. LCIS can be found in both breasts.

Although LCIS isn’t cancer, it means that you have a small increased risk of getting invasive breast cancer in either breast in the future. Even so, most women with LCIS won't develop breast cancer. Men can develop LCIS but this is very rare.

Atypical lobular hyperplasia is very similar to LCIS but with less abnormal looking cells.

How common is LCIS?

LCIS is more common in women between 45 and 50 years of age. Around 745 people are diagnosed with LCIS each year in the UK.

How is LCIS diagnosed?

LCIS doesn't usually show up on breast x-rays (mammograms), and it normally doesn't cause symptoms. It's often diagnosed by chance during tests for other breast conditions, such as a biopsy.

Please note that there is a type of breast cancer called invasive lobular breast cancer and this is different to LCIS.

Treatment for LCIS

Treatment for LCIS depends on the type you have. There are 3 main types of LCIS:

  • classic LCIS (CLCIS)
  • pleomorphic LCIS (PLCIS)
  • florid LCIS (FLCIS)

Most people with CLCIS do not need to have any treatment. But your doctor may take more breast tissue if you had a core biopsy. This is to check the area for any other changes. To remove more breast tissue you might have surgery or a vacuum assisted biopsy using a mammogram or ultrasound scan.

You usually have regular monitoring. In some situations, your doctor may offer you hormone therapy or surgery to keep your risk of developing invasive breast cancer low.

Some rarer types of LCIS such as pleomorphic LCIS or florid LCIS, are treated in a similar way to DCIS.


Your doctor might suggest that you have regular monitoring because there is an increased risk of breast cancer. They might call this close observation or careful observation.

You might have a breast x-ray (mammogram) every year for 5 years.

If a cancer does develop, the monitoring should pick it up at a very early stage. Then you can have the treatment you need as early as possible.

Hormone therapy

Your doctor may suggest taking hormone therapy for 5 years to lower your risk of developing invasive breast cancer. This is known as chemo prevention.

Many breast cancers are stimulated to grow by the female sex hormones Open a glossary item oestrogen and progesterone. These breast cancers are called hormone sensitive or hormone receptor positive.

Hormone therapy works by lowering the levels of these hormones in the body or blocking their effects.

The hormone therapy you have will depend on if you have had the menopause Open a glossary item or not. Hormone therapy drugs include:

  • tamoxifen
  • anastrozole
  • raloxifene
  • exemestane


You are more likely to have surgery rather than monitoring if you have a particular type of LCIS called pleomorphic LCIS or florid LCIS.

You might have breast conserving surgery (a wide local excision) to remove the LCIS and a surrounding area of normal tissue. Rarely you have surgery to remove your breast (a mastectomy). You might have this if the changes are widespread throughout the breast.

Research and clinical trials

Research has focused on trying to find genetic changes that might increase the risk of developing LCIS. Trials have shown that some of the known genetic changes that increase the risk of breast cancer, also increase the risk of developing LCIS.

Researchers are also looking into using different types of hormone therapy to prevent invasive breast cancer after a diagnosis of LCIS.

The IBIS 2 prevention trial followed post menopausal women who took the hormone therapy, anastrozole (Arimidex), for 5 years. This included some women with LCIS. Results showed that taking hormone therapy for 5 years did reduce the risk of developing breast cancer if you are at high risk of developing it.

  • Early breast cancer: ESMO clinical practice guidelines for diagnosis, treatment and follow up
    F Cardoso and others
    Annals of Oncology, 2019. Volume 30, Issue 8, Pages 1194 to 1220

  • Breast cancer in situ 
    E R Sauter
    BMJ Best Practice, last updated February 2023

  • UK national survey of management of breast lobular carcinoma in situ
    R Chester and others
    Annals Royal College of Surgeons, November 2015. Volume 97, Issue 8, Pages 574 to 577

  • Lobular carcinoma in situ: diagnostic criteria and molecular correlates
    A Sokolova and S R Lakhani
    Modern Pathology, January 2021. Volume 34, Supplement 1, Pages 8 to 14

  • Morphologic subtypes of lobular carcinoma in situ diagnosed on core needle biopsy: Clinicopathologic features and findings at follow-up excision
    M G Kuba and others
    Modern Pathology, August 2021. Volume 34, Issue 8, Pages 1495 to 1506

  • The information on this page is based on literature searches and specialist checking. We used many references and there are too many to list here. Please contact patientinformation@cancer.org.uk with details of the particular issue you are interested in if you need additional references for this information.

Last reviewed: 
08 Feb 2024
Next review due: 
08 Feb 2027

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