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Updated: Feb 29 2024

Chondroblastoma

Images
https://upload.orthobullets.com/topic/8021/images/Case G - femur - T2 MRI - Parsons_moved.png
https://upload.orthobullets.com/topic/8021/images/Case H- tibia- xray - Parsons_moved.jpg
https://upload.orthobullets.com/topic/8021/images/Case H - tibia MRI - parsons_moved.gif
https://upload.orthobullets.com/topic/8021/images/Histology B - Parsons_moved.png
https://upload.orthobullets.com/topic/8021/images/Histology A_moved.png
  • 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 of 10 and 20 years 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 curettage and bone grafting.
  • 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 the skeletally immature
        • 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
      • chondroblasts produce areas of chondroid matrix, but type II collagen is not expressed by tumor cells
    • 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
          • similar to giant cell tumor in this regard
          • treatment may be observation or surgical resection
      • secondary Aneurysmal Bone Cyst (ABC)
        • up to 1/3 of chondroblastomas have areas of secondary ABC
  • Presentation
    • Symptoms
      • progressive pain at tumor site
    • Physical examination
      • tenderness over the affected bone
      • decreased range of motion of the affected joint, possibly with an effusion
      • limping
      • local muscle atrophy
  • Imaging
    • Radiographs
      • recommended views
        • AP, lateral, and oblique of involved area
      • chest radiographs
        • evaluate for possible metastatic lesions
      • findings
        • lytic epiphyseal lesion
          • a geographic, well-circumscribed, oval or round lytic lesion of the epiphysis with a thin sclerotic border that sharply demarcates the tumor from normal bone
          • lesions may cross the physis into metaphysis
        • matrix calcifications
          • internal matrix calcifications that are often only apparent on CT scan (25%-45%)
        • cortical remodeling
          • cortical expasile remodeling may be present
        • soft tissue extension
          • soft tissue extension is rare, and there is usually a thin rim of calcification from the intact periosteum
        • joint effusion
        • metaphyseal periosteal reaction
          • periosteal reaction at the metaphyseal region (there is no periosteum over the epiphysis) due to irritation from the tumor
        •  aggressive appearance
          • a small subset have a more aggressive appearance due to secondary ABC formation, which can be seen in 15 to 32% of cases
      • differential with radiographs includes other epiphyseal lesions
        • see table below under "Differential"
    • CT
      • indications
        • not required
      • findings
        • defines bony extent of lesion
        • may show stippled calcifications of the cartilaginous matrix
    • MRI
      • findings
        • extensive edema of the bone marrow and/or soft tissues surrounding the lesion
        • fluid-fluid levels (indicates aneurysmal bone cyst)
        • intermediate signal intensity on T1
        • variable, heterogenous signal intensity on T2
        • heterogenous enhancement with gadolinium
    • 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 
          • sheets of intermediate-sized round to polygonal mononuclear cells (chondroblasts) with well defined borders
            • large, central nuclei with longitudinal grooves ("coffee bean" nuclei) are classic
            • a fine network of pericellular "chicken wire" dystrophic calcification is characteristic
            • chondroblasts are positive for vimentin, neuron-specific enolase, S100+, and Sox9
            • scarce mitotic figures
        • multinucleated osteoclast-type giant cells
          •  scattered multinucleated osteoclast-type giant cellsare almost uniformly present among the chondroblasts
        • amorphous chondroid matrix
          • islands of amorphous chondroid matrix are typical
            • mature hyaline cartilage is uncommon
  • 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 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
          • rarely indicated as there are no medical therapies for chondroblastoma and chondroblastomas do not heal spontaneously
    • Operative
      • intralesional curettage and bone grafting
        • indications
          • standard of care for most lesions
            • chondroblastomas do not heal spontaneously
      • radiofrequency ablation
        • indications
          • limited data to support this method of management
            • small series have shown RFA of small tumors to be effective when the location of the tumor provided limited risk of mechanical collapse of the adjacent articular surface
      • wide excision
        • indications
          • some tumors, such as those in the ribs, may best be treated with en bloc resection
      • endoprosthetic reconstruction or amputation
        • indications
          • reserved for destructive, aggressive recurrences (rare)
      • surgical resection
        • indications
          • pulmonary metastasis
  • Technique
    • Intralesional curettage and bone grafting
      • approach
        • the entire tumor should be excised by intralesional excision through a cortical window
        • the physis should be spared if possible
      • technique
        • bone graft
          • bone graft should be used to fill the cavitary defect after curettage
        • local adjuvant treatment
          • local adjuvant treatment  should be used to decrease risk of recurrence
          • modalities include
            • electrocautery
            • phenol
            • argon beam coagulation
            • and/or cryotherapy
  • Complications
    • Local recurrence
      • incidence
        • local recurrence rate is 10-15% after treatment
      • treatment
        • surveillance xrays should be performed to monitor for local recurrence
    • Limb length discrepancy
      • 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
      • treatment
        • treated with surgical resection
  • Prognosis
    • Survival
      • considered a benign curable disease
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