Atypical ductal hyperplasia (ADH)

by Jason Wasserman MD PhD FRCPC
August 3, 2022

What is atypical ductal hyperplasia?

Atypical ductal hyperplasia (ADH) is a precancerous condition in the breast. It starts from cells normally found inside small spaces called ducts.

Is atypical ductal hyperplasia cancer?

No, ADH is not a type of breast cancer. However, having ADH is associated with an increased chance of developing breast cancer in the future. Current studies suggest that a person diagnosed with ADH is 3 to 5 times more likely to develop breast cancer in their lifetime compared to someone who is not diagnosed with ADH. However, the overall risk of developing breast cancer with ADH alone is still low.

What are the symptoms of atypical ductal hyperplasia?

Most patients with ADH do not have any symptoms and the condition is found when an imaging test such as mammography is performed on the breast. ADH cannot usually be felt as a lump in the breast unless it is associated with a tumour.

What causes atypical ductal hyperplasia?

ADH is a hormone-sensitive disease which means that the cells grow and divide in response to stimulation by hormones such as estrogen. For this reason, ADH is believed to be caused by the same genetic and environmental conditions that cause hormone-sensitive types of breast cancer.

How is the diagnosis of atypical ductal hyperplasia made?

The diagnosis of ADH is usually made after a small sample of breast tissue is removed in a procedure called a biopsy. The tissue is then sent to a pathologist for examination under the microscope. The diagnosis can also be made when a larger area of breast tissue is removed in a procedure called an excision or resection. In this case, ADH is usually an incidental finding which means it is found by accident while looking for another condition.

What does atypical ductal hyperplasia look like under the microscope?

ADH is considered a ‘proliferative lesion’ which means your pathologist will see an increased number of abnormal cells inside small spaces called ducts. The abnormal cells are often described as monotonous which means they all look the same. Small deposits of calcium called microcalcifications may also be seen. If a test called immunohistochemistry is performed, the cells are often positive for estrogen receptor (ER) and progesterone receptor (PR). These proteins allow the cells in ADH to respond to the hormones estrogen and progesterone.

What is the difference between atypical ductal hyperplasia and ductal carcinoma in situ?

ADH looks similar to low grade ductal carcinoma in situ (DCIS) when examined under the microscope. However, the area of the breast involved by ADH is smaller than DCIS and may not fill the entire duct. Because ADH and DCIS look very similar, it can be very challenging for a pathologist to tell the difference between ADH and DCIS when a small sample of tissue such as a biopsy is examined.

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