Lobular carcinoma in situ (LCIS) of the breast

What is lobular carcinoma in situ?

Lobular carcinoma in situ (LCIS) is a non-cancerous breast disease. It is characterized by an increased number of abnormal epithelial cells inside the glands of the breast. Although LCIS is not a type of cancer, it is associated with an increased risk of developing breast cancer over time. The two types of breast cancer associated with LCIS are invasive ductal carcinoma and invasive lobular carcinoma. The increased risk applies to both breasts, not just the breast diagnosed with lobular carcinoma in situ.

The breast

Adult breast tissue is made up of small structures called glands which are arranged into groups called lobules. Under certain conditions, these glands can produce milk, which is transported to the nipple by a series of small channels called ducts.

The inside of both glands and ducts is lined by specialized cells called epithelial cells which form a barrier called the epithelium. The tissue surrounding glands and ducts is called stroma and contains long, thin cells called fibroblasts.


How do pathologists make this diagnosis?

The diagnosis of LCIS is usually made after a small sample of tissue is removed in a procedure called a core needle biopsy. LCIS is also commonly diagnosed after surgery is performed for another disease such as invasive ductal carcinoma or ductal carcinoma in situ.

Types of lobular carcinoma in situ

There are two different types of LCIS based on how the cells look when examined under a microscope.

  1. Classic type – This is the most common type of LCIS. The cells are small and they travel through the tissue as single cells (they are not attached to the other abnormal cells).
  2. Pleomorphic type – The cells in the pleomorphic type are larger and more abnormal-looking than the cells in the classic type. The nucleus of the cell (the part of the cell that holds most of the genetic material) is also darker and larger than the nucleus in the classic type.

Both classic and pleomorphic LCIS are associated with an increased risk of breast cancer but the risk is higher if the cells are pleomorphic.


Necrosis is a type of cell death. Comedonecrosis is a special type of necrosis sometimes seen in LCIS. In comedonecrosis, the dead cells are in the centre of a duct and surrounded by living cells. Comedonecrosis is more likely to be seen in pleomorphic LCIS. It is also associated with an increased risk of cancer compared to LCIS without comedonecrosis.​

by Jason Wasserman, MD PhD FRCPC (updated July 21, 2021)
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