Chondroblastoma is a rare tumor that usually forms at the articular ends of bones. It usually has a benign character, in the initial stages it is asymptomatic, accompanied by unpleasant sensations or minor pains that persist for several months or even years. With an increase, there is pain and swelling in the joint area. With malignancy, there is an intense pain syndrome, a pathological fracture is possible. The X-ray picture may be non-specific, therefore, CT or MRI is often required to clarify the diagnosis. Surgical treatment, resection of the neoplasm is indicated, in some cases with bone grafting or the installation of an endoprosthesis.
D16 Benign neoplasm of bones and articular cartilage
Chondroblastoma is a benign tumor formed from cartilage tissue cells. It is usually localized in the area of the epiphyses of long tubular bones. The distal epiphysis of the femur occupies the first place in terms of prevalence, the second is the proximal epiphysis of the tibia, the third is the proximal epiphysis of the humerus. Less often, chondroblastomas are found in the proximal epiphysis of the femur, pelvic bones and foot bones (especially the heel and talus). Cases of the development of chondroblastomas in the sternum, ribs, scapula, spine, patella, forearm bones, collarbone, finger phalanges, wrist bones, mandible and cranial vault bones are also described.
The greatest number of cases of the disease is detected in the second decade of life, less often the disease develops in adulthood and old age. In various age groups, chondroblastoma accounts for from 1% to 3-4% of the total number of benign tumors. Men suffer 1.5-2 times more often than women.
Chondroblastoma originates from chondroblasts and resembles a sufficiently mature cartilage tissue in its structure. The causes of tumor transformation of cells have not been established. Usually there is a slow growth and a favorable course, however, individual cases of malignancy and primary malignant course of chondroblastomas are described in the literature.
Researchers in the field of clinical oncology distinguish benign and malignant forms of chondroblastoma. The benign form can be typical or mixed. In the latter case, along with cartilage tissue cells, it has an unusual structure or contains cells characteristic of other benign tumors. The following options are possible:
- Chondroblastoma with osteoblastoclastoma.
- Chondroblastoma with chondromyxoid fibroma.
- Chondromic form of chondroblastoma.
- Cystic form of chondroblastoma.
Malignant forms of chondroblastoma are divided into:
- Malignant chondroblastoma. In this case, chondroblastoma can transform into chondroblastic osteogenic sarcoma or chondrosarcoma.
- Primary malignant chondroblastoma.
- Light-cell chondrosarcoma.
All malignant forms of chondroblastoma together account for about 7% of the total number of cases of the disease, of which 4.4% are due to malignancy of a primary benign tumor. In most cases, malignancy occurs after several relapses of the benign form of chondroblastoma, which are the result of its incomplete removal.
With a benign course in the early stages, unpleasant sensations occur in the joint area, which can persist for several months or even years. Subsequently, a progressive pain syndrome develops. The pain increases at night and during physical activity. It is possible to restrict movements with the development of contracture and moderate muscle atrophy. In some cases, pathological fractures are observed, with which patients can turn to an orthopedic traumatologist. During the examination, there is swelling in the joint area, pain during palpation and movements. When the distal femur is affected, some patients have a small effusion in the knee joint.
Malignant chondroblastomas are characterized by a rapidly progressive course with swelling and deformation of the affected area, severe pain syndrome and a high probability of pathological fractures.
Radiographs reveal a limited illumination of an ovoid or spherical shape, usually located on the lateral surface of the epiphysis. When spreading to the tendon plate, its complete destruction is noted. The pathological focus has smooth, clear contours. Along the edge of the focus, a moderately pronounced rim of sclerosis is revealed. The cortical layer of the bone is slightly swollen, periosteal layers may be detected in the area of the bone metaphysis. In about half of the cases, there is more or less pronounced mottling in the area of the focus, due to the deposition of lime in the chondroblastoma tissue.
When a chondroblastoma is localized in the region of the border between the epiphysis and metaphysis, the X-ray picture may resemble an inflammatory process (Brody’s abscess). With chondroblastoma mixed with a giant cell tumor, the focus is located in the bone, almost completely occupying it in the transverse direction and causing swelling and thinning of the cortical layer around the circumference of the bone. With the chondromic form of chondroblastoma, large foci of calcification are detected, with cystic – multiple cysts separated by partitions.
For primary malignant and malignant chondroblastoma, extensive foci of destruction with destruction of the cortical layer of bone are characteristic. In some cases, chondroblastoma radiologically resembles a giant cell tumor of bone, chondrosarcoma or osteogenic sarcoma, therefore, additional studies are required to clarify the diagnosis – trepanobiopsy or radioindication.
Macroscopically, chondroblastoma is a cartilage-like reddish-brown or gray easily crumbling tissue interspersed with denser calcified areas. Histological examination reveals densely arranged rounded and polygonal immature cells of cartilage tissue with light vesicular nuclei, resembling a picture of a “cobblestone pavement” in appearance. Large or small foci of calcification are located among these cells. Calcification sites are usually necrotic, hemorrhages can be detected near the foci of necrosis and multinucleated giant cells can be detected.
Differential diagnosis is performed with enchondroma, light-cell chondrosarcoma, giant cell bone tumor, chondromyxoid fibroma, bone cyst, Langerhans cell histiocytosis, and chondroblastic osteosarcoma. In doubtful cases, the final diagnosis is established on the basis of the results of histological examination of the biopsy.
A surgical operation involving complete removal of the tumor is indicated, since when even a small area of altered tissue is left, chondroblastoma usually recurs. Surgical intervention is performed by an oncologist on a planned basis, the volume of the operation depends on the size and localization of the chondroblastoma. With small chondroblastomas, marginal resection is performed, followed by replacement of the defect with the patient’s own bone or an allograft. If the tumor is located in the immediate vicinity of the subchondral plate, electrocoagulation of this area may be required after removal of pathologically altered tissue.
With large chondroblastomas accompanied by significant destruction of the articular end of the bone, resection of the articular end is performed with replacement of the defect with an endoprosthesis or a similar articular articular allograft. In case of malignancy and primary malignant chondroblastomas, an extended surgical intervention is performed. Often, crippling operations are required – amputations and exarticulations.
Irradiation with chondroblastoma is not indicated either in the benign course or in the case of malignancy, since a benign tumor after irradiation can degenerate into a malignant one, and with malignant chondroblastoma this treatment method is ineffective.
Prognosis and prevention
The prognosis for benign chondroblastoma is favorable, for malignant – unfavorable, however, the small number of described cases of primary malignant and malignant chondroblastoma does not make it possible to reliably predict the course and outcome of the disease. Prevention has not been developed.