summary Enchondromas are benign latent cartilaginous tumors composed of hyaline cartilage that typically occur in medullary cavity of the diaphysis or metaphysis. Patients typically present between the ages of 20-50 with an asymptomatic lesion, discovered incidentally on radiographs. Diagnosis is made radiographically with the presence of a well-defined, lucent, central medullary lesion that is 1-10 cm, and often associated with "pop-corn" stippling, arcs, whorls, or rings. Treatment is observation as most lesions are asymptomatic. Epidemiology Incidence 2nd most common benign cartilage lesion (osteochondroma is most common) Demographics male:female ratio is 1:1 age bracket most common in 20-50 year olds Anatomic location usually found in the medullary cavity of the diaphysis or metaphysis the most common locations hand (60%) > feet the most common primary bone tumor in the hand is the enchondroma other locations include distal femur (20%) > proximal humerus (10%) > tibia Etiology Pathophysiology invole IDH-1 & IDH-2 gene enchondromas represent incomplete endochondral ossification chondroblasts and fragments of epiphyseal cartilage escape from the physis, displace into the metaphysis and proliferate there malignant transformation in <1% to chondrosarcoma Associated conditions Ollier's disease (multiple enchondromatosis) sporadic inheritance with no genetic predisposition skeletal dysplasia with failure of normal endochondral ossification enchondromas throughout the metaphyses and diaphyses of long bones login to view 1 more bullet risk of malignant transformation <30% Maffucci's syndrome sporadic inheritance with no genetic predisposition distinguished by soft-tissue angiomas Marked expansion of lesion on radiographs, with angiomas are seen as small, round calcified phleboliths increased risk of visceral malignancies (astrocytoma, GI malignancy) login to view 1 more bullet Presentation Symptoms asymptomatic, discovered incidentally on radiographs usually true for enchondromas in long bones and foot pathologic fracture often seen with enchondromas in the hand pain pain is uncommon more likely in hand and feet secondary to pathologic fractures differentiates from chondrosarcomas (non-mechanical pain rest pain and nocturnal pain) Physical exam shortening and angular deformities (in inherited diseases) enchondromas may disrupt the growth plate multiple bluish angiomas in Maffucci's syndrome Imaging Radiographs usually diagnostic findings well defined, lucent, central medullary lesions that calcify over time 1 to 10cm in size login to view 2 more bullets "pop-corn" stippling, arcs, whorls, rings minimal endosteal erosion (<50% width of cortex) cortical expansion and thinning may be present in hands, feet (inherited diseases) login to view 1 more bullet skeletal survey if polycystic disease is suspected Ollier's disease login to view 1 more bullet Maffucci's syndrome login to view 1 more bullet unlike chondrosarcomas cortical thickening and destruction endosteal erosions and scalloping >50% of the width of the cortex are larger (>5cm) Bone scan indications help differentiate from chondrosarcoma to identify polyostotic disease rarely adds useful information login to view 2 more bullets findings increased uptake due to continued remodeling within lesion login to view 1 more bullet MRI lobule and bright on T2 without marrow edema or periosteal reaction indications usually not necessary for diagnosis identify size and intramedullary extent and soft tissue extension differentiate from chondrosarcoma and bony infarcts findings lobular and bright on T2-weighted images no bone marrow edema or periosteal reaction may show steak of cartilage or "sled runner tracks" medullary fill >90% suggests chondrosarcoma instead Studies Core needle-biopsy from areas of bone scalloping or lysis prone to sampling error due to tumor heterogeneity chondrosarcomas may contain areas of benign hyaline cartilage often impossible to differentiate from low-grade chondrosarcoma Histology gross appearance blue gray, lobulated hyaline cartilage, with scattered calcifications microscopic mature hyaline cartilage lobules separated by normal marrow solitary lesions in long bones login to view 4 more bullets solitary lesions in small tubular bones and fibula login to view 1 more bullet characteristics of chondrocytes login to view 3 more bullets unlike chondrosarcomas hypercellularity, with plump nuclei multiple binucleate cells giant cells with clumps of chromatin Differential Bone infarct "smoke up the chimney" radiographic appearance MRI has low T2 signal Chondrosarcoma deep endosteal scalloping >2/3 of cortical thickness more common in pelvis, scapula, ribs Treatment Nonoperative observation treatment for vast majority of asymptomatic enchondromas follow up login to view 2 more bullets Operative intralesional curettage and bone grafting indications login to view 7 more bullets outcomes login to view 1 more bullet Complications Malignant transformation risk of transformation of enchondroma to chondrosarcoma solitary enchondroma login to view 1 more bullet Ollier's disease login to view 1 more bullet Maffucci's syndrome login to view 1 more bullet