Review Question - QID 4695

The clinical presentation is consistent with an apophyseal chondroblastoma of the greater tuberosity of the humerus.

Chondroblastomas are rare lesions that occur in the epiphysis of long bones, and less commonly in the apophysis, and are thought to arise from secondary ossification centers. They rarely occur after physeal closure. The most common location is the knee (distal femur and proximal tibia), and the proximal humerus is a distant third. The natural history of this lesion is progressive bone destruction.

Sailhan et al. reviewed chondroblastomas in children. They found sex, radiographic aggressiveness, presence of ABC-component, and the method of surgical treatment had no significant influence on recurrence. Epiphyseal lesions had a higher risk of recurrence compared with metaphyseal, apophyseal, and epiphyseal-metaphyseal lesions. Lesions near the most-active physis (close to the knee or far from the elbow) were associated with a lower risk of recurrence.

Figure A shows a lytic lesion in the greater tuberosity demonstrating sclerotic margins and a stippled matrix. There is no periosteal reaction. Figure B is an axial CT showing cortical thinning at the greater tuberosity. Figure C shows classic "cobblestone" or "geometric" appearance of chondroblasts (right), with large open chromatin of the nuclei, the intervening chondroid protein (seen as red staining proteinaceous material) and the scattered phagocytic giant cells, as well as focal areas of chondroid matrix (left).

Incorrect Answers:
Answers 1, 2, 4, 5: The imaging and histological picture are not consistent with enchondroma, Ewing sarcoma, osteosarcoma or osteoblastoma.