​​Lobular carcinoma in situ (LCIS) is caused by abnormal cells forming within the milk glands (lobules) in the breast. It is most common in women between the ages of 40 nd 50. LCIS is not a cancer but it does increase the risk of developing breast cancer.

There are no known causes.

Lobular carcinoma in situ (LCIS) by itself does not usually cause symptoms but it is usually diagnosed after a biopsy is done for some other reason. In more than 50 percent of cases, Lobular Carcinoma in Situ may be multifocal, that is multiple lobules may have areas of abnormal cell growth.

​Risk factors include:

• A family history of breast cancer
• Taking hormonal replacement therapy (HRT) for menopause

Lobular carcinoma in situ (LCIS) is commonly an incidental finding on biopsy of the breast for another reason.

​Management of Lobular Carcinoma in Situ includes:

• Close observation e.g. clinical breast examinations, annual mammograms or MRI of the breasts.
• Chemoprevention, which is taking medication to reduce the risk of cancer. These drugs may include Tamoxifen or Raloxifene for 5 years.
• Surgery, where preventive or prophylactic mastectomy may be considered if there is a high risk based on a strong family history of breast cancer or if there is a BRCA gene mutation.

Cancer Risk of Lobular Carcinoma in Situ

There is an increase of 20 percent cancer risk over 15 years at the point of diagnosis.