 | The routine radiograph demonstrates a large osteolytic lesion ballooning the medial cortex of the femur, with extension into the medullary canal. The hip joint is normal. Some thickening of the medial femoral cortex is noted. The most likely diagnosis is aneurysmal bone cyst. Open biopsy reveals vascular tissue, multinucleated giant cells, and new bone. The wound was extended after biopsy, and an intralesional excision of the mass was performed. |
 | The bone lab radiograph reveals the extent of the excision. The lesion in the femur was thoroughly curetted and partially resected. Mild bleeding occurred, which was easily controlled. |
 | Histosection of the mass demonstrates many vascular spaces lined by epithelial cells. New areas of hemorrhage and new bone are seen. The solid tissue between the spaces is made of benign fibrous tissue, multinucleated giant cells, and new areas of hemorrhage and new bone. This is quite typical of a primary aneurysmal bone cyst. |
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