summary Chondroblastomas are rare, benign chondrogenic lesions that are most commonly found in the epiphysis of the proximal tibia and distal femur. Patients typically present between the ages of 10 and 20 years with regional pain. Diagnosis is made with biopsy showing chondroblasts arranged in "cobblestone" or "chickenwire" pattern with focal areas of chondroid matrix. Treatment is usually extended intralesional curettage and bone grafting. Epidemiology Demographics M:F = 2:1 80% of patients under 25 years of age Anatomic location epiphyseal lesion in young patients (usually around 12 years of age) common locations include distal femur and proximal tibia >>> proximal humerus, proximal femur, calcaneus, flat bones and apophysis or triradiate cartilage of the pelvis typically epiphyseal but may occasionally cross the physis Etiology Pathophysiology thought to arise from cartilaginous epiphyseal plate categorized as cartilage tumor due to its areas of chondroid matrix, but type II collagen is not expressed by tumor cells Genetics mutations may have genetic abnormalities on chromosome 5 and 8 Associated Conditions medical conditions & comorbidities < 1% develop benign pulmonary metastasis (similar to giant cell tumor) Presentation Symptoms progressive pain at tumor site limping Physical examination inspection muscle atrophy tenderness over affected bone motion decreased ROM Imaging Radiographs recommended views AP, lateral, and oblique of involved area findings well-circumscribed epiphyseal lytic lesion with thin rim of sclerotic bone that is sharply demarcated from normal medullary cavity lesions often cross physis into metaphysis stippled calcifications within the lesion may or may not be present (25%-45%) cortical expansion may be present soft tissue expansion rare chest radiographs evaluate for possible metastatic lesions differential with radiographs giant cell tumor osteomyelitis clear cell chondrosarcoma CT indications not required defines bony extent of lesion MRI findings extensive edema surrounding lesion Studies Histology findings chondroblasts arranged in "cobblestone" or "chickenwire" pattern may be present scattered multinucleated giant cells with focal areas of chondroid matrix occasional multinucleated giant cells may be present mononuclear stromal cells are distinct, S100+ cells with large central nuclei nuclei have longitudinal groove resembling coffee bean 1/3 of chonroblastomas have areas of secondary ABC Differential Chondroblastoma differential Epiphyseal lesion Benign lesion that may metastasize to lung Treatment is curettage and bone grafting Chondroblastoma o o o Giant Cell Tumor o o o Aneurysmal bone cyst o Osteoblastoma o Chondromyoid fibroma (CMF) o Treatment Operative extended intralesional curettage and bone grafting indications standard of treatment in symptomatic individuals technique may do local adjuvant treatment with phenol or cryotherapy to decrease local recurrence surgical resection indications pulmonary metastasis Prognosis Local recurrence rate is 10-15% after treatment