What is chondroblastoma?
Chondroblastoma is a rare, benign bone tumor comprised of cells that produce cartilage, known as chondroblasts. It is usually found in the epiphysis (ends) of long bones, usually of the lower extremity. The most common sites are the distal femur (thigh bone), proximal humerus (upper arm bone) and proximal tibia (shin bone). Sometimes it is found in the iliac crest or acetabelum (socket) of the hip.
The tumor appears more often in males than females and tends to occur during the second decade of life. Most of the time, it occurs before skeletal maturity (when full growth potential of the bones is achieved).
The tumor is considered benign, yet it may not always behave that way. Chondroblastoma is one of the few benign bone tumors that have the potential to metastasize (spread) to the lungs.
What causes chondroblastoma?
Chondroblastoma occurs when a single chondroblast (cell that produces cartilage) abnormally divides out of control. Why this occurs is unknown. There is apparently no association between chondroblastoma and repeated trauma.
What are the symptoms of chondroblastoma?
Each child experiences the symptoms of chondroblastoma differently depending on its size and location. The following are the most common symptoms associated with the condition:
- Ongoing pain, usually severe, in the affected area
- Joint stiffness
The symptoms of chondroblastoma are similar to symptoms of other medical conditions. Always consult a physician for a diagnosis.
How is chondroblastoma diagnosed?
In addition to a taking a complete medical history and performing a full physical examination, your child's doctor may use a combination of the following tests to diagnose chondroblastoma:
- X-rays - a diagnostic test that uses invisible electromagnetic energy beams to produce images of internal tissues, bones, and organs onto film.
- Magnetic Resonance Imaging (MRI) - a diagnostic procedure that uses a combination of large magnets, radiofrequencies and a computer to produce detailed images of organs and structures within the body. This test is particularly useful to confirm the diagnosis and assist in determining the exact proximity of the tumor to the bone's growth plate and adjacent joint.
- Computerized Tomography scan (also called CT or CAT scan) - a diagnostic imaging procedure that uses a combination of x-rays and computer technology to produce cross-sectional images (often called slices) both horizontally and vertically, of the body. A CT scan shows detailed images of any part of the body, including the bones, muscles, fat and organs. CT scans are more detailed than general x-rays. This test is also useful to confirm the diagnosis and assist in determining the exact proximity of the tumor to bone's growth plate and adjacent joint.
- Bone Scan - a test that uses an injection of an isotope (small dose of radioactive material) that seeks out all bones of the skeleton. It tells the doctor whether there are other tumor sites.
- 7 Complete blood count (CBC) - a measurement of size, number and maturity of different blood cells in a specific volume of blood.
- Blood tests - (including blood chemistries)
Treatment for chondroblastoma:
Specific treatment for chondroblastoma will be determined by your child's physician based on:
- your child's age, overall health, and medical history
- extent of the disease
- proximity of the tumor to the bone's growth plate
- your child's tolerance for specific medications, procedures, or therapies
- how your child's physician expects the disease may progress
- your opinion or preference
Treatment of chondroblastoma will likely involve one or a combination of the following surgical procedures performed by a pediatric orthopaedic surgeon:
- Curettage: This is the most common form of treatment for chondroblastoma. Curettage is an operation during which the tumor is scraped out of the bone with a special instrument called a curette that has a scoop, loop or ring at its tip. For this procedure, surgeons make an incision in the bone to create a window. The tumor is then completely curetted.
- Bone Grafting: After curettage, sometimes the remaining cavity is packed with donor bone tissue (allograft), bone chips taken from another bone (autograft), or other materials depending on the preference of the surgeon.
- Biopsy: During the operation, doctors will take a tissue sample of the tumor so the diagnosis can be confirmed under a microscope.
- En bloc resection: If the tumor is located in the pelvis or some other sites, the operation may involve en bloc resection, which is the surgical removal of bone containing the tumor, rather than curettage. Internal fixation, with pins, may be required to restore the structural integrity of the bone.
- Percutaneous radiofrequency ablation: This is a minimally invasive procedure in which radio frequencies are passed beneath the skin through a needle to kill the tumor cells by heating them to a high temperature. This technique is done by the radiologist in a CT scan under general anesthesia. The advantage is that this is a day procedure that does not significantly weaken the bone. It quite successfully cures the tumor by heating it and relieves the pain and has much less morbidity than an operation. This method cannot be used to treat tumors of the spinal column. It has been used primarily for another benign tumor (osteoid osteoma) but recently it has been used to treat a small number of patients with chondroblastoma. The long-term results in a large number of patients are not yet known.
What is the long-term prognosis for a patient with chondroblastoma?
The long-term outlook for a patient with chondroblastoma varies from patient to patient depending on:
- the extent of the disease
- the presence or absence of metastasis to the lungs
- the size and location of the tumor
- the tumor's response to therapy
- the age and overall health of your child
- your child's tolerance for specific medication, procedures or therapies.
Generally, chondroblastoma that is caught before metastasis is usually cured with surgery. Prompt medical attention and aggressive therapy are important for the best prognosis. Continuous follow-up care is essential for a child diagnosed with chondroblastoma.