Enchondroma
Enchondromas can occur in anyone but are most common in patients between 10 and 20 years old. They are most often found in the small bones of the hand. In fact, enchondroma is the most common tumor in the hand. Enchondomas can also develop in the body's long bones, such as the femur (thighbone), tibia (shinbone), and humerus (upper arm bone).

Enchondromas are most often solitary tumors. In rare cases, however, multiple tumors can appear as part of a condition such as Ollier's disease or Maffucci's syndrome.

Single enchondromas rarely become cancerous, though the chances are a little higher in patients with Ollier's disease and Maffucci's syndrome. When enchonromas do become cancerous, they usually become a type of malignant cartilage tumor called a chondrosarcoma.

Distinguishing between a noncancerous enchondroma and the very low-grade form of a cancerous tumor can be difficult, even for orthopaedic tumor surgeons.