Study Design. A case of the solid variant of aneurysmal bone cyst affecting the posterior component of the fourth cervical vertebra is reported. Imaging studies showed an expansile destructive lesion. After curettage, autologous iliac bone grafting with posterior fusion was performed. There was no sign of local recurrence 2 years after surgery. Objectives. To emphasize the occurrence of the solid variant of aneurysmal bone cyst in the cervical spine. Summary of Background Data. The solid variant of aneurysmal bone cyst is rare, and only 12 cases occurring in the vertebrae, including 3 in the cervical vertebrae, have been reported. The condition is difficult to diagnose radiologically before biopsy or surgery. Methods. A 9-year-old girl presented with pain in the nape of the neck without any neurologic deficit. She was found to have the solid variant of aneurysmal bone cyst in the posterior component of the fourth cervical vertebra, which had destroyed the lamina and spinous process. Part of the posterior aspect of the C4 vertebral body was also involved. Curettage of the lesion was performed, and the defect in the posterior component of the vertebra was reconstructed using an autologous iliac bone graft with posterior fusion using a halo vest. Results. Magnetic resonance imaging disclosed a homogeneous low intensity mass at the lamina, spinous process, and vertebral body of C4 on T1-weighted images. The mass showed heterogeneous high signal intensity on Gd-enhanced images. Histologically, the resected specimen showed predominant fibroblastic proliferation, with minor foci of reactive osteoid formation and an area of osteoclast-like giant cells. Neither cellular atypia nor mitotic figures were evident. There was no sign of local recurrence 2 years after surgery. Conclusions. The solid variant of aneurysmal bone cyst should be included in the differential diagnosis of any lytic expansile lesion of the spine, even though it is a destructive lesion. Gd-enhanced magnetic resonance imaging may be helpful for distinguishing the solid variant-from conventional aneurysmal bone cyst.
