Lobular carcinoma in situ (LCIS)

by Jason Wasserman MD PhD FRCPC
October 18, 2022

What is lobular carcinoma in situ?

Lobular carcinoma in situ (LCIS) is a non-cancerous breast disease. 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. Another name for LCIS is lobular neoplasia in situ (LNIS).

How is the diagnosis of lobular carcinoma in situ made?

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.

What are the types of lobular carcinoma in situ?

There are two different types of LCIS, classic type and pleomorphic type. Your pathologist will determine the type based on how the abnormal cells look when examined under a microscope. Both classic and pleomorphic LCIS are associated with an increased risk of breast cancer but the risk is higher if the cells are pleomorphic.

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

Comedonecrosis is a term pathologists use to describe a group of tumour cells with necrotic (dead) tumour cells at the center of the group. Comedonecrosis is more likely to be seen in pleomorphic LCIS and it is associated with an increased risk of developing breast cancer.​

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