Chondroblastoma
Most chondroblastomas are found close to the knee joint-either at the lower end of the femur (thighbone) or the upper end of the tibia (shinbone). They are also found in the shoulder at the top of the humerus (upper arm bone). This type of chondroblastoma is often referred to as a "Codman's tumor." Less common locations for chondroblastomas include the pelvis, hip, and heel.

Chondroblastomas 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 the body's long bones contain a small section of cartilage called a growth plate. This is the area of the bone where growth occurs. When a child is fully grown, the growth plates close, hardening into solid bone. In many cases, chondroblastomas develop around the time that the growth plates start to close.

Males are twice as likely as females to develop chondroblastomas. Eighty percent of patients are under 25 years old. The tumors are very rare, accounting for only about 1 percent of all bone tumors.

Chondroblastoma is one of the few benign bone tumors with the potential to spread, or metastasize, to the lungs. Even though a more aggressive chondroblastoma may metastasize, it is still considered a benign tumor.

How serious is chondroblastoma? Why is it a problem?
Although benign and not life-threatening, chondroblastoma is a slow-growing tumor that weakens the bone and causes kids a lot of pain. Chondroblastoma is also hard to diagnose; it can cause teens and their families a great deal of frustration while doctors go through the process of ruling out other conditions with similar symptoms.