Enchondroma: Understanding Your Pathology Report

Section Editor: Bibianna Purgina MD FRCPC
October 6, 2026

An enchondroma is a common noncancerous bone tumor made of cartilage, the firm, smooth tissue found in joints. It develops inside a bone, in the hollow center where the bone marrow is.

Enchondromas grow very slowly, and many stop growing altogether. They are often found by chance on an X-ray or MRI done for another reason. Most never cause any problems and do not need treatment.

Enchondromas are usually found in adults between 20 and 50 years old, although they can occur at any age.

This article explains how an enchondroma is diagnosed and what your pathology report findings mean.

Where do enchondromas develop?

About half of all enchondromas develop in the small bones of the hands and feet, most often the fingers. They are the most common tumor of the bones of the hand.

Most of the rest develop in the long bones of the arms and legs, especially the thigh bone, the upper arm bone, and the shin bone. Enchondromas are uncommon in the pelvis, ribs, and spine.

What are the symptoms of an enchondroma?

Most enchondromas cause no symptoms. They are often found when an X-ray or MRI is done for an unrelated reason, such as a sports injury or knee pain.

In the hands and feet, an enchondroma can thin the bone enough that it breaks with a minor injury, such as jamming a finger. This is called a pathologic fracture, and it is often how an enchondroma of the hand is first discovered. Some people also notice finger swelling.

In the long bones, an enchondroma does not usually cause pain. New pain in a known enchondroma of a long bone, without an injury, is a reason to have it checked.

What causes an enchondroma?

Most enchondromas have a change in a gene called IDH1 or IDH2. This change develops in the tumor during a person’s lifetime. It is not inherited and cannot be passed on to children.

Most people have a single enchondroma. A small number of people have many, as part of one of two conditions:

Ollier disease. Many enchondromas develop, often more on one side of the body, starting in childhood. They can cause shortening or bowing of the affected bones.
Maffucci syndrome. Many enchondromas develop together with blood vessel growths in the skin and soft tissue.

Both conditions are caused by an IDH change that occurs early in development, before birth. They are not passed down in families.

How is the diagnosis made?

An enchondroma usually has a characteristic appearance on X-ray and MRI. It looks like a well-defined area inside the bone, often containing small flecks of calcium that form rings and arcs. Many enchondromas are diagnosed from imaging alone, without removing tissue.

A pathology report is produced when tissue is removed, either in a biopsy or when the tumor is scraped out of the bone in a procedure called curettage.

Under the microscope, an enchondroma is made of cartilage cells that look very similar to normal cartilage cells, arranged in rounded groups. The tumor has a clear border with the surrounding bone. It sits beside the existing bone rather than growing into its spaces.

How is an enchondroma different from an atypical cartilaginous tumor or chondrosarcoma?

An enchondroma, an atypical cartilaginous tumor, and a low-grade chondrosarcoma can look almost identical under the microscope. Separating them is one of the hardest decisions in bone pathology.

The key difference is how the tumor relates to the surrounding bone. An enchondroma has a clear border. An atypical cartilaginous tumor or chondrosarcoma grows into the spaces of the surrounding bone and wears away its inner surface.

Because small samples may not show the edge of the tumor, pathologists make this diagnosis together with radiologists, using imaging as much as the microscope. Imaging signs that raise concern include a large tumor, deep wearing away of the inner surface of the bone, or a tumor that breaks through the bone.

Enchondromas of the hands and feet often contain more cells and look more abnormal than enchondromas elsewhere, yet they almost always behave in a noncancerous way. Your pathologist considers the location.

IDH testing does not separate an enchondroma from an atypical cartilaginous tumor or chondrosarcoma, because all of them can carry the same change.

Can an enchondroma turn into cancer?

Rarely. A single enchondroma changes into a chondrosarcoma in fewer than 1 in 100 people. This is more likely for an enchondroma in a long bone or the pelvis than for one in the hands or feet.

The risk is much higher in people with Ollier disease or Maffucci syndrome, because they have so many enchondromas. People with these conditions are usually followed regularly with imaging.

What is the prognosis?

The outlook is excellent. An enchondroma is noncancerous and does not spread. Most never cause problems.

When an enchondroma is removed by curettage, it rarely comes back. A fracture through an enchondroma of the hand usually heals well, and the enchondroma can then be treated if needed.

What happens after the diagnosis?

Observation. An enchondroma that causes no symptoms does not need treatment. Doctors often monitor a long-bone enchondroma with imaging to make sure it isn’t changing.
Curettage. An enchondroma may be scraped out if it causes pain, has caused a fracture, or is large enough to weaken the bone. The space is then filled with bone graft or bone substitute.
After a fracture, a finger fracture through an enchondroma is often allowed to heal first, with the enchondroma treated afterward.
Multiple enchondromas. People with Ollier disease or Maffucci syndrome are followed by a specialist, often for life.

Questions to ask your doctor

How sure are you that this is an enchondroma rather than an atypical cartilaginous tumor?
Does my enchondroma need any treatment?
Do I need follow-up imaging, and how often?
Is the bone at risk of breaking?
What symptoms should prompt me to come back?
Do I have more than one enchondroma?