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Chondroblastoma (kŏn'drō-blā-stā'mə) is a rare type of benign (noncancerous) tumor that usually develops at the ends of long bones, such as the thighbone and upper arm bone. Although it can affect people of all ages, it most often appears in males younger than 25 years old.
Most chondroblastomas are found around the knee at the end of the femur (thighbone) or top of the tibia (shinbone). They are also commonly found at the shoulder at the top of the humerus (upper arm bone). This type of chondroblastoma is often referred to as a "Codman's tumor." Sometimes, chondroblastomas are found in the pelvis, hip, or heel.
These tumors are made up of many cells that resemble fetal cartilage, which is how they got their name ("chondro-" means cartilage). Most bones start out as cartilage. As a fetus grows, this cartilage is mostly replaced by bone. In children, the ends of long bones contain a small section of cartilage, called a cartilaginous plate (or growth plate), which is important for bone growth. Once a child has reached skeletal maturity, this cartilage has turned to bone.
Chondroblastomas are found in men twice as often as they are found in women. Eighty percent of the time, the patients are under the age of 25 years.
Chondroblastoma is one of the few benign bone tumors that have the potential to metastasize (spread) to the lungs.
The cause of chondroblastomas is not known. They are thought to arise from the cartilaginous plates in bones near joints. Chondroblastomas do not, however, produce the same type of cartilage that protects joints and makes them easier to move. There has been no proven connection between the development of chondroblastoma and exposure to chemicals or radiation or any particular activities.
Pain is the most common symptom of chondroblastoma. Because these tumors are typically found near joints, patients often see doctors because of joint pain. In many cases, over-the-counter pain medicines, like acetaminophen or ibuprofen, do not help to relieve this pain.
Other symptoms may include:
- Joint stiffness
- Muscle atrophy (wasting away of the surrounding muscle from lack of use)
- A limp
A chondroblastoma is usually small and contained within the bone, so patients do not normally see or feel a mass.
Medical History and Physical Examination
There are many aspects to the doctor's examination. Before a physical examination, your doctor will talk with you about your general health, as well as your symptoms in order to get a good history of the problem. Pain at night or pain that just does not go away is usually more concerning because this type of pain is typical of things like tumor and infection. Pain from injury usually decreases when the injured area is not being used.
During the physical examination, your doctor will look for tenderness over the bone and check your range-of-motion in the painful area.
Your doctor will order imaging and tissue tests to diagnose chondroblastoma.
X-rays. These tests visualize dense structures like bone, and are very informative in diagnosing chondroblastoma. Most chondroblastomas are small (1 to 4 cm), round tumors. In x-ray images, chondroblastomas are surrounded with white rims. Some will cause the edge of the bone to push out, but rarely do these tumors extend past the bone and into the surrounding soft tissue. About 25% to 40% of the time, x-rays will show calcifications (white spots) inside the tumor.
Computed tomography (CT) scans. These scans are more detailed than plain x-rays. They combine x-rays with computer technology to create cross-section images.
Magnetic resonance imaging (MRI) scans. These studies produce better images of soft tissues.
Biopsy. A biopsy is often necessary to confirm a chondroblastoma diagnosis. In a biopsy, a tissue sample of the tumor is taken and examined under a microscope. Your doctor may give you a local anesthetic to numb the area and take a sample using a needle. Biopsies can also be performed as a small operation.
Under a microscope, chondroblastomas have a background that looks like cartilage and a mix of cells, some of which look like cartilage-making cells (these have nuclei that look like coffee beans). Calcifications may be seen throughout the tumor in a pattern that resembles "chicken wire."
These tests will help your doctor to differentiate chondroblastoma from other tumors that have a similar appearance, such as giant cell tumor, enchondroma, aneurysmal bone cyst, infection of the bone (osteomyelitis), and clear-cell chondrosarcoma. It is very important to differentiate chondroblastoma from more aggressive tumors like chondrosarcoma.
Treatment for chondroblastomas requires surgery.
The most common method of treating chondroblastomas is with curettage. In this procedure, the tumor is scraped out of the bone. Once these tumors are curetted, it is unusual for them to return.
After curettage, your doctor may fill the hole with a bone graft — this is bone taken from a donor (allograft) or from another bone in your body (autograft). Your doctor may also use a bone cement mixture to fill the hole. Sometimes, additional chemicals (phenol or liquid nitrogen) are placed inside the bone cavity to try to reduce the risk for recurrence.
Depending on where the tumor is located, your doctor may remove the entire section of bone, rather than performing curettage. In rare cases, chondroblastomas can spread to the lung or other organ. If the tumor spreads, surgical resection of the bone, as well as the affected area of the other organ, is necessary. This will typically result in a cure.
Recurrence of the tumor is the most serious complication of treatment. Other complications include infection and, rarely, fracture of the bone through the treated area.
How long it will take to return to daily activities will vary depending on where the tumor was located and which procedure you had to remove it. Your doctor will provide you with specific instructions to guide your rehabilitation.
Chondroblastoma returns in approximately 10% of patients. If these tumors do return, they usually will do so within a few months or a few years. Your doctor will monitor you for at least a few years. Should the tumor recur, it can be treated using the same methods. Your doctor will talk to you about all the options.
The American Academy of Orthopaedic Surgeons
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