OSTEOCHONDROMA

also called exostosis solitary benign tumour that consists partly of cartilage and partly of bone. Osteochondromas are common and may develop following trauma (injury) or may have a hereditary basis. At least one type, occurring in the external ear canal (external auditory exostosis), occurs with varying frequency in different populations and is of interest to anthropologists. Osteochondromas are not serious unless they interfere with function, in which case they should be removed. Rarely, a solitary one will become malignant in adulthood, giving rise to a chondrosarcoma. It is morphologically identical with the lesions produced in osteochondromatosis. Osteochondromatosis (also called hereditary multiple exostosis, or diaphyseal aclasis) is a relatively common disorder of skeletal development in children in which bony protrusions develop on the long bones, ribs, and vertebrae. If severe, the lesions may halt bone growth, and dwarfing will result. Pressure on tendons, blood vessels, or nerves may cause other disability. Normally, such lesions cease growing at the end of puberty; reactivation of growth in adulthood may indicate malignant change, which occurs in 5 to 15 percent of cases.