A chondroma is a benign tumor made of cartilage, the firm but flexible tissue that cushions your joints and shapes structures like your nose and ears. Most chondromas grow slowly inside bones, particularly in the small bones of the hands and feet, and many people never know they have one until it shows up on an X-ray taken for something else entirely. The risk of a single chondroma becoming cancerous is estimated at up to 4%, making regular monitoring the standard approach for most cases.
Types of Chondroma by Location
Chondromas are classified by where they form, and the name changes depending on the exact spot. The most common type, called an enchondroma, grows inside the inner cavity of a bone. A periosteal chondroma (sometimes called a juxtacortical chondroma) develops on the outer surface of a bone, typically where tendons attach. A soft tissue chondroma forms entirely outside the skeleton, usually on or near the tendons, tendon sheaths, or joint capsules of the hands and feet. Periosteal and soft tissue chondromas are considerably less common than enchondromas.
Where Chondromas Typically Form
About 60% of enchondromas occur in the small bones of the hands and feet. After those, the most common sites are the long bones: the thighbone accounts for roughly 17% of cases, followed by the upper arm bone at about 7%. Enchondromas are rare in flat bones like the pelvis, ribs, and shoulder blades, and extremely rare in the bones of the face and skull.
Periosteal chondromas follow a different pattern. Half of them appear on the upper arm bone, with the small bones of the hand being the next most common location. Soft tissue chondromas, the rarest type, tend to develop in the hands and feet as well, growing on tendons or within joint capsules rather than on bone itself.
Symptoms and How They’re Found
Many chondromas produce no symptoms at all. They’re frequently discovered by accident when someone gets an X-ray for an unrelated problem, such as a wrist injury or arthritis evaluation. This is especially true in older adults, who are more likely to have imaging done for other reasons. When symptoms do occur, they typically include mild pain or swelling near the affected area. In some cases, the tumor weakens the bone enough to cause a pathological fracture, meaning a break through the weakened spot, which may be the first sign anything was there.
How Chondromas Are Diagnosed
Plain X-rays are usually the first step. Enchondromas often appear as well-defined areas within bone, sometimes with a characteristic speckled or “popcorn” pattern of calcification. Periosteal chondromas show specific signs on imaging, including scalloping of the bone surface, a thickened layer of bone underneath the tumor, and overhanging edges where the growth meets the bone.
When a chondroma is found, the challenge is confirming that it’s benign rather than a low-grade cartilage cancer called chondrosarcoma. Under a microscope, chondromas are made up of cartilage-producing cells sitting in a smooth, glassy matrix. The cells look relatively normal, without the abnormal division patterns that signal cancer. In soft tissue chondromas, mild irregularities in the cells can sometimes mimic a more aggressive tumor on imaging or biopsy, which is why doctors rely on a combination of clinical exam, imaging, and tissue analysis rather than any single test.
Treatment: Watching vs. Surgery
For small chondromas that aren’t causing any problems, careful observation with periodic imaging is the standard approach. The Musculoskeletal Tumor Society recommends X-rays every three to six months for the first two years. If the tumor stays stable for a year, imaging can shift to once a year. A total follow-up period of at least three years is generally recommended, since growth, when it does happen, tends to appear around the two-year mark on average.
Surgery becomes the recommendation when a chondroma causes pain, leads to a fracture, or measures larger than 3 to 4 centimeters, even without symptoms. The typical procedure involves scraping out the tumor from inside the bone (curettage) and filling the space with bone graft material to restore structural strength. Whether to operate on a quiet, solitary enchondroma remains a point of debate among specialists. Surgery does offer the advantage of a definitive tissue diagnosis, symptom relief, and prevention of future fractures or, in rare cases, cancerous transformation.
Risk of Becoming Cancerous
A solitary chondroma has a low risk of transforming into chondrosarcoma, estimated at up to 4%. That risk climbs significantly for people with conditions that cause multiple chondromas throughout the skeleton.
Two genetic conditions are especially relevant. Ollier disease causes multiple enchondromas, usually concentrated on one side of the body, with a typical diagnosis around age 7. Maffucci syndrome also involves multiple enchondromas but adds abnormal clusters of blood vessels, and it’s usually diagnosed a few years later, around age 11. Both conditions carry a substantially higher cancer risk. Studies reviewing hundreds of cases found that roughly half of people with either condition eventually develop a malignancy, most commonly chondrosarcoma (affecting about a third of patients in both groups). People with Ollier disease also face a notably higher risk of brain tumors, about four times the rate seen in Maffucci syndrome.
For a person with a single, stable enchondroma discovered incidentally on an X-ray, the overall outlook is excellent. The vast majority of solitary chondromas remain benign and never require treatment beyond routine monitoring.