Atypical ductal hyperplasia (ADH)

by Jason Wasserman MD PhD FRCPC and Zuzanna Gorski MD
May 1, 2024

Atypical ductal hyperplasia (ADH) is a precancerous condition in the breast. A person with this condition has a 3- to 5-fold increased risk of developing a type of breast cancer called invasive ductal carcinoma in their lifetime. This condition starts from cells normally found inside small spaces called ducts.

Is atypical ductal hyperplasia a type of cancer?

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

What are the symptoms of atypical ductal hyperplasia?

Most patients with atypical ductal hyperplasia do not have any symptoms. The condition is found when a breast imaging test, such as mammography, is performed. It cannot usually be felt as a lump in the breast unless it is associated with a tumour.

What causes atypical ductal hyperplasia?

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

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

Atypical ductal hyperplasia looks similar to low grade ductal carcinoma in situ (DCIS) when examined under the microscope. However, the area of the breast involved in this condition is smaller than DCIS and may not fill the entire duct. Because atypical ductal hyperplasia and DCIS appear very similar, it can be challenging for a pathologist to distinguish between these conditions when examining a small tissue sample, such as a biopsy.

Microscopic features of atypical ductal hyperplasia

Atypical ductal hyperplasia is a proliferative lesion, indicating an increase in abnormal cells within the small ducts. Pathologists often describe these cells as monotonous because they appear uniform (they look alike). Small calcium deposits, known as microcalcifications, may also be seen. When immunohistochemistry is performed, the abnormal cells are typically positive for estrogen receptor (ER) and progesterone receptor (PR), allowing them to respond to the hormones estrogen and progesterone.

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