Solid aneurysmal bone cyst with pathologic bone fracture

A patient is presented with solid aneurysmal bone cyst of the left proximal femur and a pathologic bone fracture in this region. The radiological and histological features of this lesion are described. While a conventional aneurysmal bone cyst is an expanding osteolytic lesion consisting of blood-filled spaces of variable size, separated by connective tissue containing bone trabeculae or osteoid tissue and many osteoclastic giant cells, a solid aneurysmal bone cyst is an unusual solid bone lesion with fibroblastic, osteoclastic, osteoblastic, aneurysmal, and fibromyoxid elements. The differential diagnosis includes giant cell tumor and fibroblastic osteosarcoma as well as specific bone reactions (bone fracture, reparative giant cell granuloma in hyperparathyroidism, giant cell reaction of short tubular bones). Solid aneurysmal bone cyst is a tumor-like lesion and probably a special bone reaction to damage; it has a good prognosis. Usually curettage is curative.