Review Question - QID 213026

Chondroblastomas are benign chondroid tumors of the epiphysis of long bones with the potential to metastasize to the lungs. Initial management should include a chest radiograph.

Chondroblastoma is a benign tumor of cartilaginous derivation seen most often in the 2nd decade of life with a male predominance. The lesion is usually centered on the epiphyseal region at the end of long tubular bones. Proximal humerus, proximal tibia, and distal femur are the most commonly involved locations. Local pain is frequently the presenting symptom. The tumor commonly spreads to the chest first, so a chest radiograph would be the next best step in treatment.

Binesh et al. wrote a case study on a patient who had a fatal case of a pure metaphyseal chondroblastoma. The patient was 9-years-old with pulmonary metastases soon after operative therapy of the primary tumor. They conclude that this was a rare case as chondroblastoma represents less than 1% of all bone tumors and it is located at the level of the epiphysis of long bones.

Xu et al. performed a retrospective multicenter study of 199 patients that were treated for extremity chondroblastoma in order to determine epidemiological characteristics. They reported the proximal tibia was the most commonly involved site followed by the proximal femur and then the distal femur. Approximately 95% of patients were treated with curettage and 5% with en bloc resection while the involvement of the proximal humerus being the only significant risk factor for local recurrence. The authors concluded that treatment with curettage and bone grafting provides favorable local control.

De Mattos et al. reviewed the epidemiology, etiology, diagnosis, and treatment of chondroblastoma and chondromyxoid fibroma. They cited literature stating that metastasis occurred in less than 1% of affected patients with the lung being the most common location of metastasis. Several studies have postulated that p53 mutation is associated with metastatic behavior of the primary tumor with most patients having a several-year survival with metastatic lesions. They concluded that surgical treatment is challenging due to the proximity to the physis and metastatic lesions having a good prognosis if they are resectable.

Illustration A is a photomicrograph of a chondroblastoma. There are pink areas of chondroid differentiation on the right and sheets of histiocyte-like tumor cells in the center and to the left with a characteristic cobblestone pattern.

Incorrect answers:
Answer 2: Enchondromas are benign cartilaginous lesions that are not associated with metastatic behavior, so chest radiographs are not indicated in the workup for these lesions.
Answer 3: Non-ossifying fibromas are eccentric metaphyseal lesions with a soap bubble appearance, which are usually an incidental finding. These lesions have no metastatic behavior and do not require advanced imaging or chest radiographs.
Answer 4: Osteochondromas are benign cartilaginous lesions that originate from the zone of Ranvier of the physis and form an exostosis. Less than 1% of these lesions can undergo malignant transformation into chondrosarcoma.
Answer 5: Unicameral bone cysts are common peri-physeal lesions that usually resolve with skeletal maturity. They are not associated with metastatic behavior and do not require a chest radiograph as part of the initial management.