Chondroblastoma
Synonyms and keywords: Codman tumor; Codman's tumor; Codman tumour; Codmans tumor; Chondroblastomas; Benign chondroblastoma; Epiphyseal chondroblastoma

# Overview
Chondroblastoma is a benign cartilaginous tumor that account for 1% of all bone tumors. Chondroblastoma typically occurs in children and adolescents between 10 and 25 years of age. Male are more commonly affected with chondroblastoma than female. The male to female ratio is approximately 2:1. The epiphysis of the distal femur, proximal tibia, and proximal humerus are the most common sites. In 1928, Codman first described chondroblastoma as epiphyseal chondromatous giant cell tumors of the proximal humerus. The exact pathogenesis of chondroblastoma is not fully understood. Various theories have been postulated such as chondroblastoma arising from osteoid matrixcontaining type I collagen and there is absence of true cartilage matrix production (type II collagen). Recently, a specific mutation in the histone 3 gene H3F3B (K36M), was identified in approximately 95% of chondroblastoma. The hallmark of chondroblastoma is pain, limping, tenderness and restricted range of motion. If left untreated, few patients with chondroblastoma may progress to develop lung metastasis. The mainstay of treatment for chondroblastoma is surgery in form of curettage and bone grafting.

# Historical Perspective
- In 1928, Codman first described chondroblastoma as epiphyseal chondromatous giant cell tumors of the proximal humerus.
- In 1942, Jaffe and Lichenstein later recognized it as a distinct entity due to its chondorid matrix.

# Classification
Chondroblastoma can be classified based on imaging findings.

## Enneking (MSTS) Staging System
- The Enneking surgical staging system (also known as the MSTS system) for benign musculoskeletal tumors is based on radiographic characteristics of the tumor host margin.
- It is widely accepted and routinely used classification.

# Pathophysiology
- The exact pathogenesis of chondroblaroma is not fully understood.
- Various theories have been proposed concerning the pathogenesis of chondroblastomas:
Chondroblastoma tumors are of chondrogenic origin.
Chondroblastoma arises from osteoid matrixcontaining type I collagen and the absence of true cartilage matrix production (type II collagen).
Chondroblastoma arises from an intraosseous proliferation of tendon sheath cells that have a predilection for chondroid formation.
- Chondroblastoma tumors are of chondrogenic origin.
- Chondroblastoma arises from osteoid matrixcontaining type I collagen and the absence of true cartilage matrix production (type II collagen).
- Chondroblastoma arises from an intraosseous proliferation of tendon sheath cells that have a predilection for chondroid formation.
- Chondroblastomas typically occur in the epiphyses and apophysis of the long bones.
- The bones often involved by epiphyseal chondroblastomas are femur, tibia, and humerus.

## Genetics
- Chondroblastoma may have association with genetic abnormalities on chromosome 5 and 8.
- Recently, a specific mutation in the histone 3 gene H3F3B (K36M), was identified in approximately 95% of chondroblastomas.

# Causes
There are no established causes for chondroblastoma.

# Differentiating Chondroblastoma from Other Diseases
- Chondroblastoma must be differentiated from following bone disorders:

# Epidemiology and Demographics
- Chondroblastoma is a rare benign bone tumor accounting for approximately 1% of all benign bone tumors.
- Adolescents and children are most affected by chondroblastoma.
- The age distribution of chondroblastoma is between 10-25 years with the mean age being 22 years.
- Men are more commonly affected than women, with a 2:1 ratio.
- There is no racial predilection to chondroblastoma.

# Risk Factors
There are no established risk factors for chondroblastoma.

# Screening
There is insufficient evidence to recommend routine screening for chondroblastoma.

# Natural History, Complications, and Prognosis
- If left untreated, few patients with chondroblastoma may progress to develop lung metastasis.
- Common complications of chondroblastoma include:
Pathological fracture
Premature epiphyseal closure
Limb-length discrepancy
Angular deformity
Malignant transformation
Metastasis to other organs
Metastasis most frequently involves the lungs and tends to occur at the time of primary tumor recurrence.
Other sites of metastasis are secondary bone sites, soft tissue, skin, or liver.
- Pathological fracture
- Premature epiphyseal closure
Limb-length discrepancy
Angular deformity
- Limb-length discrepancy
- Angular deformity
- Malignant transformation
- Metastasis to other organs
Metastasis most frequently involves the lungs and tends to occur at the time of primary tumor recurrence.
Other sites of metastasis are secondary bone sites, soft tissue, skin, or liver.
- Metastasis most frequently involves the lungs and tends to occur at the time of primary tumor recurrence.
- Other sites of metastasis are secondary bone sites, soft tissue, skin, or liver.
- Depending on the extent of the tumor at the time of diagnosis, the prognosis may vary. However, the prognosis is generally regarded as excellent.
- Factors that influence the outcome of the chondroblastoma include:
Extent of the tumor
Size and location of the tumor
Pulmonary metastasis
Tumor response to the therapy
- Extent of the tumor
- Size and location of the tumor
- Pulmonary metastasis
- Tumor response to the therapy

# Diagnosis

## Diagnostic Study of Choice
- X-ray is the diagnostic study of choice for the diagnosis of chondroblastoma.
- X-ray findings include:
Well-circumscribed eccentric oval or round lytic lesion that usually involves the adjacent bone cortex without periosteal reaction.
A sclerotic margin can be observed in some cases.
For long bone chondroblastoma the tumor is typically contained to the epiphysis or apophysis but may extend through the epiphyseal plate.
A mottled appearance on the radiograph indicates areas of calcification which is commonly associated with skeletally immature patients.
In cases involving older patients or flat bones, typical radiographic presentation is not as common and may mimic aggressive processes.
- Well-circumscribed eccentric oval or round lytic lesion that usually involves the adjacent bone cortex without periosteal reaction.
- A sclerotic margin can be observed in some cases.
- For long bone chondroblastoma the tumor is typically contained to the epiphysis or apophysis but may extend through the epiphyseal plate.
- A mottled appearance on the radiograph indicates areas of calcification which is commonly associated with skeletally immature patients.
- In cases involving older patients or flat bones, typical radiographic presentation is not as common and may mimic aggressive processes.

## History and Symptoms
Symptoms of chondroblastoma include:
- Localized bone pain with activity and rest
Pain often present for months or years; frequently misdiagnosed as chronic synovitis
- Pain often present for months or years; frequently misdiagnosed as chronic synovitis
- Localized swelling
- Decreased range of motion of the affected joint
- Limp

## Physical Examination
- Patients with chondroblastoma usually appears well.
- Common physical examination findings of chondroblastoma include:
Tenderness to palpation
- Tenderness to palpation
- Soft tissue swelling
Decreased range of motion
Muscle atrophy
Joint effusion
- Soft tissue swelling
- Decreased range of motion
- Muscle atrophy
- Joint effusion

## Laboratory Findings
There are no diagnostic laboratory findings associated with chondroblastoma.

## Electrocardiogram
There are no ECG findings associated with chondroblastoma.

## X-ray
- Three views of affected bone or joint are recommended.
- X-ray findings include:
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.
- 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 X-Ray
- Chest radiograph should be done to look for benign pulmonary metastasis which may occasionally may occur with chondroblastoma.

## Echocardiography or Ultrasound
There are no echocardiography/ultrasound findings associated with chondroblastoma.

## CT scan
CT findings for chondroblastoma include:
- Lacelike matrix mineralization along with scalloped borders.
- Periosteal reaction.
- It also defines bony extent of the lesion.

## MRI
- MRI of chondroblastoma is ideal for the evaluation of transphyseal or transcortical extension, and for demonstrating associated surrounding bone marrow and soft tissue edema, which is observed in a large proportion of cases.
- MRI Findings include:
- The lesions have signal typical of cartilage:
T1: low to intermediate signal
T2: intermediate to high signal
Focal lobules of low, intermediate, and high signal intensity most likely correspond to calcification, chondroid matrix, and fluid in the lesion.
MRI may also reveal an effusion of the joint.
Fluid-fluid levels may occasionally be observed presumably due to an associated aneurysmal bone cyst.
- The lesions have signal typical of cartilage:
T1: low to intermediate signal
T2: intermediate to high signal
- T1: low to intermediate signal
- T2: intermediate to high signal
- Focal lobules of low, intermediate, and high signal intensity most likely correspond to calcification, chondroid matrix, and fluid in the lesion.
- MRI may also reveal an effusion of the joint.
- Fluid-fluid levels may occasionally be observed presumably due to an associated aneurysmal bone cyst.

## Other Imaging Findings
There are no other imaging findings associated with chondroblastoma.

## Other Diagnostic Studies

## Biopsy
- Biopsy may be helpful in the diagnosis of chondroblastoma.
- Biopsy grossly demonstrates the following features:
Irregularly lobulated, hemorrhagic, bluish gray, and gritty lesions that expands the epiphysis.
- Irregularly lobulated, hemorrhagic, bluish gray, and gritty lesions that expands the epiphysis.
- On histological examination:
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.
One-third of chonroblastomas have areas of secondary aneurysmal bone cyst.
- 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.
- Nuclei have longitudinal groove resembling coffee bean.
- One-third of chonroblastomas have areas of secondary aneurysmal bone cyst.

# Treatment

## Medical Therapy
There is no treatment for chondroblastoma; the mainstay of therapy is surgery.

## Surgery
Surgery is the mainstay of treatment for chondroblastoma.

## Extended Intralesional Curettage and Bone Grafting
Indications
- Symptomatic individuals.
Technique
- Local adjuvant treatment with phenol or cryotherapy to decrease local recurrence.

## Radiofrequency Ablation
- Another procedure that may be used for the management of chondroblastoma is radiofrequency ablation which is less invasive and has less recovery time.
- Radiofrequency ablation is typically most successful for small chondroblastoma lesions about 1.5 cm.

## Surgical Resection
Indications
- Pulmonary metastasis.

## Recurrence
- Local recurrence rate is 10-15% after treatment.

## Primary Prevention
There are no established measures for the primary prevention of chondroblastoma.

## Secondary Prevention
There are no established measures for the secondary prevention of chondroblastoma.