Chondroblastoma

A chondroblastoma (most often found in pediatric patients) is a rare type of noncancerous bone tumor that begins in the cartilage. Most  are found around the knee at the end of the thighbone or top of the shinbone. They’re also commonly found at the shoulder, but can occur in the pelvis, hip or heel. These tumors are very rare, but chondroblastoma is one of the few benign bone tumors with the potential to spread, or metastasize, to the lungs. 

Types & Stages

The types of chondroblastoma depend on their location in the body and include:

• Most chondroblastomas. Found close to the knee joint — either at the lower end of the femur (thighbone) or the upper end of the tibia (shinbone). Less common locations for chondroblastomas include the pelvis, hip and heel.
   
• Codman's tumor. Found in the shoulder at the top of the humerus (upper arm bone). 

Signs & Symptoms

The most common symptom of a chondroblastoma is joint pain. A chondroblastoma is usually small and contained within the bone, so you won’t normally see or feel a mass. 

Other signs and symptoms of may include:
•    pain at night or pain that doesn’t go away with rest
•    joint stiffness
•    joint swelling
•    muscle atrophy (wasting away of the surrounding muscle from lack of use)
•    a limp (when the tumor is in the lower extremities)

Diagnosis

Tests and procedures used to diagnose a chondroblastoma include:

• Imaging tests. These may include: 
   
  • X-rays. X-rays provide images of dense structures, such as bone, and are very helpful in diagnosing chondroblastomas. Most are small (1 to 4 centimeters), round tumors immediately adjacent to the ends of bones. On X-ray images, they’re often surrounded by a thin rim of white bone. Some will cause the edge of the bone to push out, but rarely do the tumors extend past the bone and into the surrounding soft tissue.
     
  • Bone scans. A whole-body bone scan is a nuclear medicine test to check your bones for issues or changes. You receive an injection of a substance called a radiotracer. The radiotracer collects in areas of irregular activity and highlights these areas on an imaging scan. 
     
  • Computerized tomography scan (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. 
     
  • 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. 
     
• Biopsy. A biopsy is often necessary to confirm the diagnosis of chondroblastoma. In a biopsy, a sample of tissue is taken from the tumor and examined under a microscope. 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 weaving throughout the tumor in a pattern that resembles chicken wire.

Treatment

Without treatment, a chondroblastoma will likely continue to grow and destroy the surrounding bone, so treatment is almost always necessary. This includes:

• Surgery. Procedures to remove the tumor and prevent damage to the end of the affected bone include: 
   
  • Curettage and bone grafting. This is the most common treatment for chondroblastomas. During this procedure, 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. The remaining cavity is usually filled with donor bone tissue (allograft) or bone chips taken from another bone in your child's body (autograft). The graft takes two or three months to heal into the bone.
     
  • Extended curettage. In some cases, orthopedic surgeons perform an “extended” curettage using a special instrument to remove additional layers of cells around the chondroblastoma. This is done to reduce the risk of recurrence.
     
  • En bloc resection. A surgeon may need to surgically remove bone containing the tumor if it’s located in the pelvis or certain other sites. They may insert pins and other hardware (internal fixation) to restore the structural integrity of the bone.
     
• Nonsurgical treatment. When more extensive surgery might lead to unacceptable complications, options may include:
   
  • Radiofrequency ablation. In this procedure, the tumor is heated and destroyed with a high-frequency electrical current. This procedure works best for small lesions.
     
  • Cryotherapy. In this procedure, the tumor is destroyed using extreme cold produced by liquid nitrogen.

Causes & Risk Factors

They tend to occur in males and females between ages 10 and 20. 

Screening

There is no specific screening test for chondroblastomas.