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Updated: Apr 10 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 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
          • 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
      • 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
          • 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
    • CT
      • CT of lesion/involved area
        • indications 
          • not required, but can be useful if 3-dimensional anatomy is distorted or complex
        • findings
          • defines bony extent of lesion
          • may show stippled calcifications of the cartilaginous matrix
      • CT chest
        • indications
          • CT chest should be considered if chest radiographs show any signs of metastases
    • 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 
          • 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
            • recurrent lesions may show cellular atypia that shouldn't be confused with malignant transformation
        • multinucleated osteoclast-type giant cells
          •  scattered multinucleated osteoclast-type giant cells are 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 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
          • rarely indicated as there are no medical therapies for chondroblastoma and chondroblastomas do not heal spontaneously
    • Operative
      • intralesional curettage and bone grafting with local adjuvant
        • indications
          • standard of care for most lesions
            • chondroblastomas do not heal spontaneously
        • techniques
          • local adjuvant therapy
            • should be given to prevent local recurrence
            • modalities include
              • phenol
              • hydrogen peroxide
              • argon beam coagulation
              • cryotherapy
      • radiofrequency ablation
        • indications
          • can be considered as a first-line treatment as there is good success with similar recurrence rate as intralesional curettage
          • MRI hallmarks of success include necrosis beyond tumor margin and resolution of perilesional edema
      • 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 of pulmonary metastases
        • indications
          • solitary or oligometastases
          • those with numerous metastases can be treated with denosumab with good long-term outcomes
  • 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
          • bone graft should be used to fill the cavitary defect after curettage
          • dependent on location, structural osteochondral graft may be needed for weight bearing surfaces
        • local adjuvant treatment
          • local adjuvant treatment  should be used to decrease risk of recurrence
          • examples include cryotherapy, phenol, and hydrogen peroxide
  • Complications
    • Local recurrence
      • incidence
        • local recurrence rate is 10-15% after treatment
          • this includes both surgical and RFA techniques
          • purely epiphyseal lesions recur at a significantly higher rate than epiphyseal-metaphyseal, apophyseal, and metaphysical only lesions
      • 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
          • permeative growth pattern and significant cellular atypia are characteristic findings
      • treatment
        • wide surgical resection is standard of care
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