Enchondroma (en-kon-DRO-ma) is one type of benign (noncancerous) cartilage tumor that appears on the inside of the bone. These tumors usually begin and grow in childhood, then stop growing but remain present throughout adulthood. They are often found in patients between 10 and 20 years of age. Some cases become dormant or burned out.Description
These tumors are very common and often occur in the small bones of the hand and feet. In fact, they are the most common tumor of the hand. They also occur in the long bones of the upper arm and thigh.
In rare cases, multiple tumors can appear as part of a syndrome. These syndromes are Ollier's disease and Maffucci's syndrome.
Single enchondromas can become cancerous, but this is very rare. The rate of change to a cancerous tumor is a little higher in Ollier's disease and Maffucci's syndrome. For the very few that become cancer, when they become malignant, they usually become a chondrosarcoma. Being able to tell the difference between these benign tumors and very low-grade forms of cancerous tumors can be difficult, even for orthopaedic tumor surgeons.Cause
The cause of enchondromas is not completely clear, but they don't seem to be caused by exposure to chemicals or radiation or patient activities.Symptoms
These tumors are usually painless. When these tumors appear in the hands or feet, or in multiple lesions, they can deform the bone. The symptoms for enchondromas of the hands and feet are enlarged fingers, pathologic fracture, or deformities.
The deformities in patients with Ollier's disease and Maffucci's syndrome can be quite severe. If pain from other nearby sources has been excluded, the tumor should be carefully studied to determine whether it could be a low-grade chondrosarcoma. Pain at night or at rest is more likely to mean a malignant tumor. But pain is also very common with some shoulder conditions like rotator cuff tendonitis.Doctor Examination
Plain radiograph (left) and magnetic resonance image (right) showing a large enchondroma of the fifth metacarpal of the hand.
Most enchondromas are found when x-rays are taken for another reason, such as injury or arthritis. The diagnosis of an enchondroma is important. This is to make sure that it is not a more aggressive or cancerous tumor.
In addition to imaging tests, the physician evaluates the medical history and physical examination findings. It is important to know if the tumor is painful and the kind of pain it causes. There is greater concern if the pain occurs at rest or if the pain occurs at night and does not go away. Pain caused by activity is not as troublesome.
The next most important information is found on the x-rays. Enchondromas appear as small (less than 5 cm) lobe-shaped, white tumors in the middle of the bone. The white areas of the tumor usually show a pattern of rings and arcs that indicates the tumor contains cartilage.
Most enchondromas are diagnosed on plain X-rays. On an X-ray, they appear as a dark hole in the bone, but usually they have calcification or white spots in the hole.
X-rays showing a benign enchondroma. Anteroposterior (left) and lateral (right) X-rays show a benign enchondroma discovered when X-rays were done after a knee injury.
A computed tomography (CT) or magnetic resonance imaging (MRI) scan of the affected bone may sometimes be helpful. These scans give a more complete picture of the bone around the tumor.
Enchondroma of the upper arm. Coronal (left) and axial (right) magnetic resonance images of a painful tumor in the upper arm (humerus).
Bone scans can be helpful in some circumstances. However, both benign and malignant tumors can show increased uptake of the radioactive tracer used to detect increased bone activity.
Bone scan showing slight uptake in the near the end of the thighbone (femur). This is the same patient whose X-rays are seen in the above figure.
Under the microscope, enchondromas have islands of cartilage that are easy to tell apart from the normal bone that surrounds them. Usually, cartilage is not found in the center of bones. However, these tumors in the hand and foot or in Ollier's disease or Maffucci's syndrome may contain more odd-looking cartilage. They may be more difficult to tell apart from a mildly cancerous malignant tumor called low-grade chondrosarcoma.
Low-grade chondrosarcomas (cancers) look more cellular under a microscope than enchondromas and there is less normal bone in the tumor. Because both low-grade chondrosarcomas and enchondromas look similar under the microscope, a group effort between experienced surgeons, radiologists, and pathologists is important to get the best interpretation of the tumor.
Characteristics of a more aggressive tumor or malignant chondrosarcoma include:
Treatment Nonsurgical Treatment
Most enchondromas require no treatment at all. When needed, treatment for enchondroma can vary. This sometimes causes debate, even among orthopaedic oncology surgeons due to the difficulty in determining the aggressiveness of the lesion.
Lesions that show no symptoms can be watched with regular x-rays to ensure the tumor is not growing. Most surgeons think that tumors without symptoms do not need to be removed.Surgical Treatment
When enchondromas are treated surgically, it is usually with scraping out and filling of the cavity with bone graft or other filling substances. Although they can come back (recur), most of them will not.
Tumors that cause pathologic fractures are usually treated by allowing the fracture to heal. Then, the tumor is scraped out to prevent another fracture.
More aggressive tumors with bone destruction or with a mass growing outside the bone are usually chondrosarcomas. These tumors need to be removed.
Malignant tumors are either scraped out or the entire bone around the lesion must be removed. This decision is made depending on the grade of the tumor. The grade of the tumor is determined by imaging studies and biopsy.
Methods of treating tumors that look like simple enchondromas on x-ray studies, but are painful, can be controversial. Some surgeons recommend that the tumor be scraped out.
Other surgeons think that these tumors do not require surgical removal. This is because they are not likely to be the cause of the pain in the area and so should be observed with regular x-rays.
Unfortunately, a biopsy will not often help in these cases. Even specialized bone pathologists can have trouble determining the difference between a benign enchondroma and a low grade chondrosarcoma.Research on the Horizon
There is a lot of ongoing research on enchondromas and chondrosarcomas. Ongoing studies are trying to identify chemical markers that can tell doctors the difference between benign and malignant cartilaginous tumors.