osteochondroma

An osteochondroma is a type of benign bone tumor. Most of these tumors are discovered as a hard protruberance from a long bone (bone of the arm or leg). As a rule, they are nonpainful. They consist of a bony core covered by a cartilage "cap." These tumors so rarely turn malignant in childhood that they are usually left alone unless they cause pain or are growing rapidly.

An alternate name for an osteochondroma is an exostosis. There is a rare syndrome of multiple hereditary exostoses which, as the name implies, involves multiple osteochondromas. These children may have other orthopedic problems as well, including extremity deformities, short stature, and unequal limb lengths.