Review Question - QID 218722

The patient has a chondroblastoma, as evidenced by the classic histology seen in Figure C, which is best treated with extended intralesional curettage and bone grafting +/- an adjuvant when symptomatic.

Chondroblastomas represent rare, benign chondrogenic lesions that are most commonly found in the epiphyses of the proximal tibia and distal femur. They occur most often in males between the ages of 10 and 20, often with the chief complaint of regional pain that is progressive and may cause a reduced range of motion and a limp. Though the lesions are most frequently located in the epiphyseal region of the bone, they often cross the physis into the metaphysis. Radiographs will show a well-circumscribed, lytic lesion with a thin rim of sclerotic bone that is sharply demarcated from the normal medullary cavity with or without stippled calcifications and cortical expansion (Figures A and B). The histology seen after biopsy (Figure C) is classic, with chondroblasts arranged in a "cobblestone" or "chickenwire" pattern among scattered multi-nucleated giant cells and focal areas of chondroid matrix. Mononuclear stromal cells are also seen, which have characteristic nuclei with a longitudinal groove resembling a "coffee bean." The differential diagnosis for chondroblastoma should include giant cell tumor (GCT), osteoblastoma, and aneurysmal bone cyst (ABC). Treatment is operative and includes extended intralesional curettage and bone grafting +/- local adjuvant (phenol or cryotherapy) to decrease recurrence risk. Overall recurrence is 10-15% after treatment.

Cho et al. published a review of nine patients with chondroblastomas of the proximal tibia treated with curettage, bone grafting, and cementation. The authors found no local recurrence or pulmonary metastasis at a mean duration of follow-up of 47.2 months. They concluded that intralesional curettage followed by additional burring with cementation through an extra-articular approach is a successful treatment option for chondroblastoma of the proximal tibia.

Liu et al. reviewed 36 patients with chondroblastoma of the adjoining knee joint, all of whom were treated with intraregional aggressive curettage, phenolization, and allogeneic bone grafting. They were followed out to a mean of 518 months and were assessed for functional outcomes and rates of secondary osteoarthritis. The authors found good bone healing in all patients without varus or valgus deformity, mean Musculoskeletal Tumor Society functional scores of 28.6 ± 1.1, and secondary arthritis in only one patient who was asymptomatic. They concluded that intraregional aggressive curettage, phenolization, and allogeneic bone grafting are effective for the treatment of chondroblastoma of the adjoining knee joint.

Figures A and B are AP and lateral radiographs of the knee demonstrating the classic radiographic appearance of an epiphyseal chondroblastoma. Figure C represents the classic histology seen in chondroblastoma with chondroblasts arranged in a "chickenwire" fashion.

Incorrect Answers:
Answer 2: Medical management with denosumab can be used to stabilize lesions in patients with Giant Cell Tumors of bone, not chondroblastoma.
Answer 3: Neoadjuvant chemotherapy, wide resection, and adjuvant chemotherapy is the treatment protocol for malignant bone lesions, such as osteosarcoma, not benign lesions like chondroblastoma.
Answer 4: Observation with serial radiographs is indicated in benign, non-aggressive lesions such as enchondromas, not chondroblastomas.
Answer 5: Radiation followed by wide resection and adjuvant chemotherapy is a treatment option for many soft tissue sarcomas, not for benign primary bone tumors such as chondroblastomas.