This article was last reviewed on August 13, 2019 by Jason Wasserman, MD PhD FRCPC
The normal 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.
What is lobular carcinoma in situ?
Lobular carcinoma in situ is not a cancer. However, the diagnosis of lobular carcinoma in situ is associated with an increased risk of developing breast cancer over time. The increased risk applies to both breasts, not just the breast diagnosed with lobular carcinoma in situ.
The diagnosis of lobular carcinoma in situ is usually made after a small sample of tissue is removed in a procedure called a core needle biopsy. Lobular carcinoma in situ 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 lobular carcinoma in situ based on how the cells look when examined under a microscope.
Why is this important? Both classic and pleomorphic lobular carcinoma in situ are associated with an increased risk of breast cancer but the risk is higher if the cells are pleomorphic.
The nucleus is the part of the cell that contains most of the cells genetic material (the DNA). The abnormal cells in lobular carcinoma in situ are given a nuclear grade between 1 and 3 based on the shape and size of the nuclei and the number of abnormal cells dividing to creating new cells (mitotic figures).
Instead of a numerical grade (1 through 3), some pathology reports divide the grade in low, intermediate, and high.
Why is this important? The nuclear grade is important because grade 3 (high grade) lobular carcinoma in situ is associated with a higher risk of cancer compared to grade 1 (low grade) lobular carcinoma in situ.
Necrosis is a type of cell death. Comedonecrosis is a special type of necrosis sometimes seen in lobular carcinoma in situ. In comedonecrosis, the dead cells are in the centre of a duct and surrounded by living cells.
Why is this important? Comedonecrosis is more likely to be seen in high grade lobular carcinoma in situ. It is also associated with an increased risk of cancer compared to lobular carcinoma in situ without comedonecrosis.