Chondroblastoma is defined per WHO as a ” relatively benign tumor, characterized by high cellular and relatively undifferentiated tissue, made up of round or polygonal chondroblast like cells with distinct outlines and multinucleated giant cell of osteoclast type arranged in singly or in groups. The presence of a cartilaginous intracellular matrix with areas of focal calcification is typical.
It is 1 % of all primary bone tumors which is epiphyseal / Apophysial in origin.
Etiology of Chondroblastoma
Chondroblastoma arises from the secondary center of ossification so it is epiphyseal/metaphyseal in origin.
Traditionally Chondroblastoma is called to be chondrogenic in origin but contains osteoid matrix and Type I collagen and there is the absence of true cartilage matrix production. So some prefer it to say bone-forming tumor.
Structural abnormality is seen in Chromosome numbers 5 and 8.
Male: Female:: 2:1
Site
Epiphyseal/ Apophyseal is the common site which is near the growth plate.
Chondroblastoma is the most common tumor occurring in patella
Talus and calcaneum ( Foot) is the second common site.
Clinical Features
Pain and swelling in and around the affected joint.
The onset is more severe and rapid compared to other benign bone tumors.
Radiological Features
Chondroblastoma is well defined lytic area adjacent to the epiphyseal line.
It is a thin, lobulated, sclerotic margin (Unlike GCT)
It may cross physis so sometime it is presented in the metaphysis.
In around 30% of cases, there is matrix mineralization due to secondary calcium deposition.
The periosteal reaction may be present.
If there is the presence of multiple fluid levels it is due to secondary ABC.
Pathology
Gross:
Dark red or fan colored with yellow zones of calcification are seen.
Microscopic:
Pericellular type of calcification: Chicken wire pattern
Chicken wire is diagnostic of Chondroblastoma
Scattered osteoclast-like giant cells
A large sheet of compact round polygonal cells is seen.
Treatment of Chondroblastoma
Intralesional curettage with appropriate reconstruction is done
En-bloc excision is done for multiple recurrent tumors and with extraosseous component or articular degeneration is seen.
Recurrences
Recurrences of 15-20 % are seen mostly in the first and second years.
Pulmonary Metastasis is seen in recurrent tumors.
Post-radiation sarcoma may be seen.
See also: Enchondroma
See also: Musculoskeletal Malignancy: Management
