Osteochondromas usually stop growing at the time of growth plate closure. Symptomatic tumors are cured by simple excision. Rarely in sporadic cases, but more commonly in those with multiple hereditary exostosis (5%– 20%), osteochondromas progress to chondrosarcoma.
Chondromas are benign tumors of hyaline cartilage that usually occur in bones of endochondral origin. They arise within the medullary cavity (enchondroma) or on the cortical surface (juxtacortical chondroma). Enchondromas are usually diagnosed in individuals 20 to 50 years of age. Typically, they appear as solitary metaphyseal lesions of the tubular bones of the hands and feet. The radiographic features consist of a circumscribed lucency with central irregular calcifications, a sclerotic rim, and an intact cortex (
Fig. 21.21 ). Ollier disease and Maffucci syndrome are disorders characterized by multiple enchondromas (enchondromatosis). Maffucci syndrome also is associated with other rare tumors.
Most enchondromas of large bones are asymptomatic and are detected incidentally. Occasionally, they are painful and cause pathologic fracture. The tumors in enchondromatosis may be numerous and large, producing severe deformities, especially of the digits.
Fig.21.21Enchondromaoftheproximalphalanx.Theradiolucentnoduleofcartilagewithcentralcalcificationthinsbutdoesnotpenetratethecortex.
http://ebooksmedicine.net
Heterozygous gain of function mutations in the IDH1 and IDH2 genes, coding for the enzymes isocitrate dehydrogenases, have been identified in the chondrocytes of syndromic and solitary enchondromas. Patients with enchondroma syndromes are mosaics, harboring IDH mutations in only a subset of otherwise normal cells throughout their bodies. The mutations confer a new enzymatic activity on the IDH proteins that leads to the synthesis of 2-hydroxyglutarate. As discussed in Chapter 6, this so-called “oncometabolite” interferes with regulation of DNA methylation and is also implicated in certain glial tumors and a subset of acute myeloid leukemias.
MORPHOLOGYEnchondromasareusuallysmallerthan3cmandaregray-blueandtranslucent.Theyarecomposedofwell-circumscribednodulesofhyalinecartilagecontainingbenignchondrocytes(
Fig.
21.22 ).Theperipheralportionofthenodulesmayundergoendochondralossification,andthecentercancalcifyandinfarct.Syndromicenchondromasaresometimesmorecellularwithmoreatypiathansporadicenchondromas.
The growth potential of chondromas is limited. Treatment depends on the clinical situation and usually includes observation or curettage. Solitary chondromas rarely undergo sarcomatous transformation, but those associated with enchondromatosis do so more frequently. Individuals with Maffucci syndrome also are at risk of developing other neoplasms, including brain gliomas.