by Ashley Flaman MD and Bibianna Purgina MD FRCPC
November 10, 2023

An enchondroma is a common non-cancerous type of bone tumour made up of cartilage. Enchondromas are usually found in the bones of the hands or feet, but they may occur in almost any bone in the body. They usually affect young and middle-aged adults. Although very rare, a small percentage (less than 1%) of all enchondromas can turn into a type of cancer called chondrosarcoma over time.

What are the symptoms of an enchondroma?

In most cases, enchondromas do not cause symptoms and are often found when imaging (such as an X-ray or CT scan) is performed for another reason. When they do cause symptoms, pain or enlargement of the affected area is most common.

What causes an enchondroma?

Most enchondromas are associated with a mutation (genetic change) in the gene for IDH1 or IDH2. The altered gene leads to the production of an abnormal protein which results in tumour growth over time.

How is this diagnosis made?

The diagnosis can be made after a small tissue sample is removed in a procedure called a biopsy or when the entire tumour is removed in a procedure called a resection or curettage. In some cases, the diagnosis can be made without a tissue examination because the appearance on imaging is unique. Because they are not cancerous and many grow either very slowly or not at all, some patients may choose, along with their surgeons, not to have the tumour removed.

What does an enchondroma look like under the microscope?

Under the microscope, an enchondroma is made up of specialized cells called chondrocytes which are the cells that make cartilage. The chondrocytes and matrix (the tissue that surrounds the chondrocytes) in an enchondroma look very similar to normal cartilage. At the edge of the tumour, there is a clear border between the tumour and the surrounding normal bone tissue. This feature is important because a type of bone cancer called chondrosarcoma can look similar to an enchondroma under the microscope.

In contrast to an enchondroma, the border between chondrosarcoma and the normal bone is less clear as the tumour cells in chondrosarcoma spread into and destroy the surrounding bone. This spread into normal bone can also be seen when imaging such as an X-ray is performed. For this reason, your pathologist may also look at your X-ray or other imaging results to make sure there is no bone destruction before making the diagnosis of enchondroma.

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.

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