summary Chondroblastomas are rare, benign but locally destructive tumors of immature cartilage-forming cells (chondroblasts) that arise almost universally in the epiphysis of long bones. Patients typically present between the ages in 3rd decade of life with regional pain and/or a limp. Diagnosis is made with biopsy showing chondroblasts arranged in a "chickenwire" pattern with foci of chondroid matrix and scattered multinucleated osteoclast-type giant cells. Treatment is usually intralesional resection, local adjuvant therapy (i.e. cryoablation), +/- bone graft Epidemiology Demographics rare (~1% of osseous neoplasms) M:F = 2:1 predominantly occur in the immature skeleton 80% of patients under 25 years of age Anatomic location almost exclusively arise in the epiphysis of skeletally immature long bones common locations include the proximal humerus, proximal femur, distal femur, and proximal tibia can cross the physis into the metaphysis may also arise from an apophysis; from the patella, from the talus or calcaneous in the feet ("epiphyseal equivalents"), or from flat bones Etiology Pathophysiology bengin proliferation of immature cartilage cells (chondroblasts) that are locally destructive thought to arise from cartilaginous epiphyseal plate, but histogenesis is controversial chondroblasts produce areas of chondroid matrix, but hyaline cartilage is rarely produced Recurrent chondroblastomas can show cellular atypia, but this is usually not equivalent to malignant transformation Genetics no principally defining mutations mutations in histone H3.3 are described abnormalities on chromosomes 5 and 8 are common Associated conditions pulmonary metastasis <1% develop "benign" pulmonary metastasis login to view 2 more bullets secondary Aneurysmal Bone Cyst (ABC) up to 1/3 of chondroblastomas have areas of secondary ABC Presentation Symptoms pain progressive pain at tumor site joint stiffness limp Physical examination local muscle atrophy tenderness over the affected bone decreased range of motion of the affected joint, possibly with an effusion Imaging Radiographs recommended views AP, lateral, and oblique of involved area chest radiographs login to view 1 more bullet findings lytic epiphyseal lesion login to view 2 more bullets matrix calcifications login to view 1 more bullet cortical remodeling login to view 1 more bullet soft tissue extension login to view 1 more bullet joint effusion metaphyseal periosteal reaction login to view 1 more bullet aggressive appearance login to view 1 more bullet differential with radiographs includes other epiphyseal lesions CT CT of lesion/involved area indications login to view 1 more bullet findings login to view 2 more bullets CT chest indications login to view 1 more bullet MRI findings extensive edema of the bone marrow and/or soft tissues surrounding the lesion intermediate signal intensity on T1 variable, heterogenous signal intensity on T2 heterogenous enhancement with gadolinium fluid-fluid levels (indicates secondary aneurysmal bone cyst) Bone scan indications not required findings chondroblastomas demonstrate increased radionuclide uptake, especially in the uninvolved bone adjacent to the tumor Studies Histology findings polygonal mononuclear chondroblasts login to view 6 more bullets multinucleated osteoclast-type giant cells login to view 1 more bullet amorphous chondroid matrix login to view 2 more bullets Differential Chondroblastoma almost exclusively occurs in the epiphysis and should be high on the differential for a young person with an epiphyseal lesion the differential for chondroblastomas chiefly includes other ephiphyseal or apophyseal lesions diagnosis must be confirmed with a biopsy Differential tables Chondrogenic Lesions BENIGN Radiographic Presentation Characteristic Histology Treatment Enchondroma Most common in patients 20 to 50 years old Well defined, lucent, central medullary lesions. Blue gray, lobulated hyaline cartilage, with scattered calcifications. Observation Periosteal chondroma Most common in patients 10 to 30 years old Well-demarcated, shallow cortical defect Similar to enchondroma (bland hyaline cartilage with small chondroid cells except for increased cellularity and more malignant looking cells. Marginal excision Solitary Osteochondroma Most common in patients 10 to 30 years old Pedunculated lesions on bone surface with continuity of cortex Similar to a normal physis with hyaline cartilage cap and well-defined perichondrium. Observation if asymptomatic Chondroblastoma Most common in patients 10 to 30 years old Lytic epiphyseal lesion Chicken wire" dystrophic calcification with sheets of polygonal mononuclear chondroblasts Intralesional curettage and bone grafting. Chondromyxoid fibroma Age at diagnosis typically ranges from 10-30 years Lobulated, eccentric lytic lesions with sclerotic borders Assortment of chondroid, myxoid, and fibrous tissue with stellate cells in a pseudolobulated architecture Intralesional curretage and bone grafting (or PMMA) MALIGNANT Chondrosarcoma Occurs in older adults (40 to 75 years) Lytic lesions with characteristic "rings and arcs" or "popcorn calcification" Bland hyaline cartilage appearance with varying amount of cellularity based on grade Wide surgical excision Mesenchymal chondrosarcoma Occurs in younger patients (20 to 40 years) than conventional chondrosarcoma Moth-eaten or permeative lytic lesion with variable matrix calcification High-grade biphasic chondrosarcoma characterized by poorly differentiated small round blue cells and islands of hyaline cartilage Wide surgical excision May respond to chemotherapy and radiation Secondary chondrosarcoma Usually found in significantly younger patients (3rd and 4th decades) than primary conventional chondrosarcoma From osteochondroma: cartilage cap >2cm on MRI or CT with intralesional lysis of calcifications and cortical destruction Same as conventional chondrosarcoma Wide surgical excision Clear cell chondrosarcoma Occurs in younger patients (20 to 40 years) than conventional chondrosarcomas Well-defined osteolytic lesion in the epi-metaphyseal region Low-grade malignant chondrogenic neoplasm characterized by lobules of clear cells Wide surgical excision Differential Diagnosis for Epiphyseal Lesion Key Differentiating Findings Chondroblastoma (this topic) Typically skeletally immature, insidious and progressive pain, may see mineralization of cartilaginous matrix; extensive peritumoral edema on MRI Giant Cell Tumor Typically skeletally mature (age 20-40) with closed physes; originates from metaphysis but can extend into the epiphysis; pathologic fracture common Clear Cell Chondrosarcoma More common in 3rd to 5th decades of life; typically larger on presentation (>4cm); less peritumor edema on MRI than chondroblastoma; malignant Brodie abscess Typically sketally immature; often metaphyseal; signs and symptoms of infection are frequently absent; "penumbra" on MRI is characteristic Intraosseous Ganglion Typically occur in middle-age; periosteal reaction should be absent; cystic on MRI with less peri-lesional edema than chondroblastoma Eosinophilic Granuloma Variable radiographic appearance Brown Tumor Typically age >50; chronic renal disease / hyperparathyroidism Aneurysmal Bone Cyst Typically age <20; multicystic bone lesion with fluid-fluid levels on MRI; Osteoblastoma Typically 2nd and 3rd decades; rarely epiphyseal; commonly painful; may see matrix mineralization; extensive peritumoral edema on MRI Osteoid Osteoma Children and adolescents; typically diaphyseal, rarely epiphyseal; nocturnal pain relieved by NSAIDs; nidus on CT; peritumoral edema on MRI Other Metastatic disease, multiple myeloma, lymphoma Treatment Nonoperative observation alone indications login to view 1 more bullet Operative intralesional curettage and bone grafting with local adjuvant indications login to view 2 more bullets techniques login to view 7 more bullets radiofrequency ablation indications login to view 2 more bullets wide excision indications login to view 1 more bullet endoprosthetic reconstruction or amputation indications login to view 1 more bullet surgical resection of pulmonary metastases indications login to view 2 more bullets Technique Intralesional curettage and bone grafting approach the entire tumor should be excised by intralesional excision through a cortical window it is common to extend local resection with high-speed burr into healthy bone for complete excision the physis should be spared if possible technique bone graft login to view 2 more bullets local adjuvant treatment login to view 2 more bullets Complications Local recurrence incidence local recurrence rate is 10-15% after treatment login to view 2 more bullets etiology recurrence is primarily thought to occur from inadequate resection rather than a completely new lesion in the same area of complete excision treatment surveillance radiographs should be performed for 5 years to monitor for local recurrence repeat surgical intervention is warranted Limb length discrepancy etiology physis may be damaged by the tumor or by treatment treatment consider contralateral epiphysiodesis versus limb lengthening depending on the patient Degenerative joint disease incidence hip replacement and knee replacement often required in affected joint in adult ages Metastatic lung disease incidence occurs in <1% of cases treatment treated with surgical resection usually has indolent course Prognosis Survival generally considered a benign, curable disease if treated surgically or via RFA as it does not spontaneously resolve Malignant transformation incidence exceedingly rare, several case reports have been published presents later in life, median age 52 years can metastasize to lungs, bone, soft tissues of the axial and appendicular skeleton, brain histology shares some histological characteristics with chondroblastoma-like osteosarcoma, but there is no osteoid produced login to view 1 more bullet treatment wide surgical resection is standard of care