Atypical lobular hyperplasia of the breast

by Jason Wasserman MD PhD FRCPC
November 16, 2023


Atypical lobular hyperplasia (ALH) is a growth made up of abnormal cells in the breast. The abnormal cells are found inside groups of small glands called lobules. ALH is a noncancerous condition, however, it is associated with a small increased risk of developing breast cancer over time.

Is atypical lobular hyperplasia of the breast a type of cancer?

No. ALH is not a type of breast cancer. However, ALH is associated with an increased risk of developing breast cancer over time.

Is atypical lobular hyperplasia a precancerous condition?

ALH is not considered a precancerous condition because only a small number of patients who have ALH will go on to develop breast cancer over time.

What causes atypical lobular hyperplasia in the breast?

At present, doctors do not know what causes ALH.

What are the symptoms of atypical lobular hyperplasia in the breast?

On its own ALH does not cause any symptoms and the condition is normally discovered incidentally when tissue from the breast is examined under the microscope for other reasons.

How is this diagnosis made?

The diagnosis of ALH can only be made after tissue from the breast is examined under the microscope by a pathologist. The tissue may be a biopsy or a larger surgical procedure such as a lumpectomy or resection.

What does atypical lobular hyperplasia look like under the microscope?

When examined under the microscope, ALH is made up of abnormal cells that fill small glands within groups called lobules. The cells may be described as monomorphic which means they are all very similar looking. The cells may also be described as discohesive which means they are not sticking together like normal epithelial cells. Mitotic figures (cells dividing to create new cells) may also be seen.

atypical lobular hyperplasia breast
Atypical lobular hyperplasia in the breast. This picture shows a lobule is expanded by abnormal cells.

What is e-cadherin and why is it important?

E-cadherin is a protein made by most types of epithelial cells including the cells normally found in the breast. This protein is normally found on the membrane or surface of the cell. Instructions for making the e-cadherin protein come from a gene called CDH1. The function of e-cadherin is to help neighboring epithelial cells stick together.

normal e-cadherin expression in the breast
This picture shows normal e-cadherin expression in the breast. The brown cells are positive for e-cadherin.

Before making the diagnosis of ALH, your pathologist may perform a test called immunohistochemistry (IHC). This test allows the pathologist to see if the abnormal cells are producing e-cadherin. Cells that produce e-cadherin are called positive while those that are not producing e-cadherin are called negative. In most cases of ALH, the CDH1 gene has become altered which results in a loss of e-cadherin production.

This picture shows a loss of e-cadherin expression (right) in atypical lobular hyperplasia of the breast.
This picture shows a loss of e-cadherin expression (right) in atypical lobular hyperplasia of the breast.

About this article

This article was written by doctors to help you read and understand your pathology report. Contact us if you have any questions about this article or your pathology report. Read this article for a more general introduction to the parts of a typical pathology report.

Related articles on MyPathologyReport

Lobular carcinoma in situ
Invasive lobular carcinoma

Other helpful resources

Atlas of Pathology
A+ A A-