While the exact cause of enchondroma is not known, it is believed to occur either as an overgrowth of the cartilage that lines the ends of the bones, or as a persistent growth of original, embryonic cartilage.

An enchondroma may occur as an individual tumor or several tumors. The conditions that involve multiple lesions include the following:

- Ollier disease (enchondromatosis) - when multiple sites in the body develop the tumors. Ollier disease is very rare.

- Maffucci's syndrome - a combination of multiple tumors and angiomas (benign tumors made up of blood vessels).

One person in every 100,000 is affected. Ollier disease is not normally diagnosed until toddler years because it is not very visible.

Ollier disease carries a high risk of skeletal, visceral and brain malignancy which occurs in approximately 25% of patients. Juvenile granulosa cell tumour has been associated with the disease. The incidence of secondary chondrosarcoma in Ollier disease is not known, but may be as high as 25%, pelvis and shoulder girdle being the commonest locations. A related disorder called Maffucci syndrome named after Angelo Maffucci is characterized by enchondromas associated with multiple hemangiomas which usually occur in the hands and feet. Maffucci syndrome carries a higher risk for cancer.

A chondroma is a benign cartilaginous tumor, which is encapsulated with a lobular growing pattern.

Tumor cells (chondrocytes, cartilaginous cells) resemble normal cells and produce the cartilaginous matrix (amorphous, basophilic material).

Characteristic features of this tumor include the vascular axes within the tumor, which make the distinction with normal hyaline cartilage.

Based upon location, a chondroma can be described as an enchondroma or ecchondroma.

- enchondroma - tumor grows within the bone and expands it.

- ecchondroma - grows outward from the bone and this is rare.

Treatment

- best left alone

- if it causes fractures (enchondroma) or is unsightly it should be removed by curettage and the defect filled with bone graft.

A bone tumor (also spelled bone tumour) is a neoplastic growth of tissue in bone. Abnormal growths found in the bone can be either benign (noncancerous) or malignant (cancerous).

Average five-year survival in the United States after being diagnosed with bone and joint cancer is 67%.

Treatment of bone tumors is highly dependent on the type of tumor.

Prognosis depends on how early the cancer is discovered and treated. For the least aggressive grade, about 90% of patients survive more than five years after diagnosis. People usually have a good survival rate at the low grade volume of cancer. For the most aggressive grade, only 10% of patients will survive one year.

Tumors may recur in the future. Follow up scans are extremely important for chondrosarcoma to make sure there has been no recurrence or metastasis, which usually occurs in the lungs.

The cause is unknown. Patients may have a history of enchondroma or osteochondroma. A small minority of secondary chondrosarcomas occur in patients with Maffucci syndrome and Ollier disease.

It has been associated with faulty isocitrate dehydrogenase 1 and 2 enzymes, which are also associated with gliomas and leukemias.