Giant pediatric aneurysmal bone cyst of the occipital bone: a case report and review of the literature

Aneurysmal bone cyst (ABC) is an infrequent, vascular, non-neoplastic, benign tumor-like lesion of the bone first described by Jaffe and Lichtenstein in 1942 (1); the term "aneurysmal" simply describes the blow-out appearance on a radiograph. ABC is now regarded as a misnomer because it is a non-neoplastic bony lesion that consists of cystic cavernous cavities with a paucity of endothelial cell lining filled with unclotted blood. The precise etiology and pathophysiology of ABCs remain uncertain, but it is speculated that factors such as trauma, underlying neoplasms, and cytogenetic abnormalities are thought to be the possible pathophysiology of ABCs (2). The lesion can also be secondary to a reactive process following vascular hemodynamic disturbances associated with elevated venous pressure and trauma-induced hemorrhage (3). In some cases, ABCs are associated with underlying lesions such as osteoblastomas, eosinophilic granulomas, fibrous dysplasia, chondroblastomas, osteosarcomas, and chondromyxoid fibromas (4-8). Although, the lesion is classified as benign, malignant transformation has been reported in 3% of patients (9,10). Aneurysmal bone cysts represent only 1%-2% of all primary bone tumors and are usually located in the metaphyses of long bones and in the spine in 50% and 20% of cases, respectively (11). ABCs are occasionally found in the cranium, as described in 3%-6% of cases (12); in extremely rare instances, ABCs are found in the occipital region of the cranium (9,11). Treatment is often achieved by a curative en-bloc resection of the ABC and cranioplasty preferably with a titanium mesh to minimize the risk of recurrence (13). Prognosis is excellent, provided complete resection is achieved, but incomplete removal may affect its cure rate (14).