Chondroblastoma

Chondroblastoma

CHONDROBLASTOMA

General Information

Benign neoplasm of immature cartilage cell (chondroblast) proliferation

Cells resemble chondrocytes/chondroblasts

Marked predilection for arising from the epiphysis

Usually occurs in skeletally immature patients

Female 1.4:1

Age:

Range 3 - 72 years

95% of cases occur between the ages 5 and 25

Most cases occur in adolescents between 10 and 20 years of age

Sites:

Predilection for distal femur, proximal tibia & humerus

98% located in epiphysis, 30% in knee area

May also occur in calcaneus, talus and temporal bone

Most Common Sites:

Proximal Femur 23%

Distal Femur 20%

Head and Neck 16%

Trochanter 7%

Proximal Tibia 17%

Proximal Humerus 17%

Hands and Feet 10%

Radiographic Presentation

Presents as a highly defined/well circumscribed geographic oval/round lytic defect

Surrounded by rim of sclerotic bone

Usually in epiphyseal region

Lesion ranges from 3 cm to 6 cm diameter

Usually radiolucent

May have fine trabeculae and irregular calcifications

Calcifications are often better detected with a CT scan but are not uniformly present

Lesions may expand the bone and new periosteal bone may form

Bony end plate, cortex, bone contour are unaffected

Plain X-rays:

Geographic lytic lesion IA/IB margin of sclerosis

Usually Eccentric more often than Central in the bone

Rarely expansile (rarely penetrates the cortex)

Calcified chondroid matrix 30%-50% of cases

Often better detected with a CT Scan

Periosteal Reaction 30-50% of cases

Usually occurs in Adjacent Diaphysis/Metaphysis since epiphysis is intraarticular and not surrounded by periosteum

MRI:

Geographic, well circumscribed lesion in the epiphysis

Intermediate Signal on T1

High signal on T2 mixed with low signal areas (low signal areas proposed to be secondary to lysosomal content of highly cellular areas)

Fluid/Fluid levels demonstrated in tumors that have undergone ABC change (aneurysmal bone cyst change)

Extensive Surrounding edema is common

Joint effusion in 30-50% of cases

CT scan:

Most useful for detecting subtle mineralization that is not apparent on X-rays

Useful for identifying intact periosteum around any expansile soft tissue component that appears as a surrounding thin reactive shell of bone/mineralization (Egg Shell Rim of Calcification). This helps place the tumor in a benign category.

Can help evaluate bony quality, extent of bone and cortical destruction and whether the subchondral plate of bone adjacent to the joint cartilage has been destroyed or is intact.

Bone Scan:

Chondroblastomas demonstrate intense increased uptake on a bone scan

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Gross Pathology

Grossly variable appearance

Grey/yellow/brown and gritty if has interspersed calcifications

Interspersed red areas from hemorrhagic necrosis

May be blue-grey areas from the chondroid matrix

Rim of sclerotic bone is visible in totally resected specimens

Lesion may be fully cystic with solid foci of tumor tissue at periphery

May undergo aneurysmal bone cyst change (ABC change)

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Microscopic Pathology

Variable appearance depending on percentage of cells, necrosis, cartilage matrix formation and ABC change

Hypercellular Tumor; Minimal Pleomorphism; Occasional Mitoses but no Abnormal Mitoses; No Atypia

Chondroid matrix in up to 15% of tumor

ABC component 5-15% of tumors

The tumor is composed of chondroblasts that have a distinct, thick cell membrane. The thick cell membrane gives it a "Chicken Wire Fence Appearance" especially when the cell membranes are calcified. "Chicken Wire Calcifications"

Cytoplasm of chondroblasts is plump, clear, eosinophilic

Nucleus is centrally or eccentrically round/oval with indentations

Coffee Bean Shaped Nucleus

Nucleus exhibits clefts, grooves, invaginations

Cells are closely packed together

Osteoclast-like giant cells are interspersed

Calcification is an important diagnostic sign and deposits itself along cell membranes. This gives a pattern referred to as a "Chicken Wire pattern of Calcification" because the appearance is similar to a chicken wire fence.

Chondroblasts stain positive for S-100

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Biological Behavior

Chondroblastomas are benign aggressive tumors. They grow aggressively and destroy the bone.

Chondroblastomas can destroy the cortex and grow into the soft tissues. They are contained by the periosteum (this differs from a malignant tumor that destroys the cortex)

There are extremely rare cases where chondroblastomas metastasize to the lungs and may not appear for 30 years

Metastases may remain stable or may progress and cause death

Recurrences may occur in the bone or adjacent soft tissue

Rare cases of multifocal chondroblastomas have been documented

Synchronous involvement of several sites

Secondary aneurysmal bone cyst frequently correlated with chondroblastoma

Chondroblastomas have been reported to transform into fibrosarcoma or osteosarcoma years after being treated with radiation.

Treatment

Intralesional curettage resection and bone grafting is the most common treatment. Cement and internal fixation may also be used to fill the defect after removal for selected patients.

High risk of local recurrence after curettage alone

Local adjuvants such as cryosurgery (liquid nitrogen application) may be considered to decrease the risk of local recurrence.

Local recurrence results in further bony destruction

Rarely chondroblastomas that have grown out of control have required amputations for treatment because they have completely destroyed the bone and/or adjacent joint.

In patients who are skeletally immature (still growing) there is always a risk of growth plate failure from the chondroblastoma since it usually grows adjacent to the growth plate and may damage it.

CT Guided Radiofrequency Ablation (Minimally Invasive Approach)

May be indicated for selected small tumors

Mostly performed in specialized centers

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Prognosis

Chondroblastomas are benign aggressive tumors that grow and destroy the bone and joint as it grows.

Most patients are cured with the first surgery

There is a significant risk of local recurrence (up to 30% with an intralesional curettage alone without an additional local adjuvant such as cryosurgery). Microscopic tumor cells can grow back after the tumor is removed.

My preferred method is to perform curettage and cryosurgery whenever feasible in appropriate cases in order to help eradicate microscopic disease and decrease the risk of local recurrence (decrease the risk of the tumor coming back in the bone after surgery)

Radiofrequency has been successful in the treatment of very selected small tumors.

This is a minimally invasive approach

Rare cases of pulmonary metastases have been reported.

Pulmonary metastases may be stable or may progress and cause death

Pulmonary metastases have extremely rarely been reported to develop 30 years after initial treatment.