A chondroblastoma is a benign bone tumor that usually develops in children and adolescents. This type of tumor most often grows in the ends of the long bones of the legs. It usually is confined to the ends of the bone and only rarely spreads to the middle portion. In 10 percent of cases, the tumor develops in bones of the hands or feet. Chondroblastoma bone tumors are very rare, comprising about one percent of all tumors that originate in bone. It is extremely uncommon for this benign tumor to become cancerous, but it is possible for malignancy to develop.
This type of tumor arises as a result of the overgrowth of cells called chondroblasts. These cells are immature cartilaginous cells; when mature, cells of this type form the connective tissue called cartilage. Chondroblastomas are approximately twice as common in males as in females, and 90 percent of tumors are diagnosed in people between 5 and 25 years old. Although this is primarily a disease of younger people, this type of tumor has been diagnosed in individuals as old as 83. There are no known risk factors, although there are several genetic mutations thought to be associated with this type of tumor.
The most common symptom of a chondroblastoma is pain. When it first appears, this pain is mild and might be attributed to an injury such as a sprain or torn muscle. The pain tends to progress gradually, and there often are no other symptoms. Only about 20 percent of people have any noticeable swelling or lump. The absence of other symptoms often causes people to live with the pain for a year or more before seeking treatment.
Treatment for chondroblastoma typically involves surgery to remove the tumor and a small amount of surrounding tissue. To ensure that the bone remains structurally stable, tumor removal is followed by a procedure in which the empty space left behind is filled with a bone graft or a synthetic polymer. Most patients can resume normal activities once they have recovered from surgery, but the risk of complications such as graft failure, bone fracture at the lesion site and joint degeneration requires that patients continue to be monitored after the procedure.
Chondroblastoma tumors often recur after removal, with a risk of recurrence being between 10 and 35 percent. Tumors are more likely to recur when they are more than 1.45 inches (3.7 cm) in size or are secondary growths that spread from the point at which the original tumor grew. The final known risk factor is the location of the tumor. Those removed from certain parts of the femur and pelvis are more likely to regrow, because of accessibility issues that make it difficult for a surgeon to be sure he or she has removed the entire tumor.