Complex sclerosing lesion of the breast

by Kimberly Wood, MD MSc FRCPC
November 16, 2023


A complex sclerosing lesion (CSL), also known as a radial scar, is a non-cancerous growth characterized by an increased number of glands and ducts around a central scar. Although non-cancerous, CSL is associated with a small increased risk of developing breast cancer when compared to women without CSL.​

What are the symptoms of a complex sclerosing lesion?

Most complex sclerosing lesions in the breast do not cause any symptoms and the growth is found incidentally when imaging of the breast is performed for other reasons. Rarely, does the growth become large enough to be felt as a lump in the breast.

What causes a complex sclerosing lesion of the breast?

At present doctors do not know what causes this condition to develop.

How is a complex sclerosing lesion of the breast diagnosed?

Complex sclerosing lesions (CSL) can be diagnosed after a small sample of tissue is removed in a procedure called a biopsy. The diagnosis can also be made after a larger area of tissue is removed in a procedure called a resection.

For many patients, a CSL is discovered incidentally after a biopsy or resection is performed for another reason. However, some CSLs can be seen on screening mammography/ultrasound, especially when they are greater than 1 cm in size. Because a CSL can look very similar to breast cancer on mammography or ultrasound, a biopsy is performed to confirm the diagnosis.

What does a complex sclerosing lesion look like under the microscope?

When examined under the microscope, a CSL is made up of abnormal connective tissue that pathologists describe as fibrosis. The abnormal connective tissue is sometimes described as showing elastosis or being elastotic because it contains numerous elastic fibers. Small irregularly shaped ducts and glands are often seen trapped within the area of fibrosis. Other non-cancerous changes that are often seen in the tissue surrounding a CSL include usual ductal hyperplasia (UDH), cysts, and apocrine metaplasia.

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.

Other helpful resources

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