Intraosseous hibernoma: a case report and review of the literature.

STUDY DESIGN: A case report and a literature review are presented.

OBJECTIVE: To describe and review the clinical presentation and characteristic imaging and pathology findings of intraosseous hibernoma.

SUMMARY OF BACKGROUND DATA: Hibernomas are lesions of brown fat. Brown fat is typically found in newborn mammals and is rich in mitochondria, thus enabling its role in thermoregulation. It represents a small proportion of adult fat and is distinct from the more common "white fat." Rarely does a hibernoma occur within bone. To the authors' knowledge, 5 cases in all have been reported in the literature.

METHODS: We report the first case to our knowledge of an intraosseous hibernoma occurring within the lumbar spine as well as a review of the literature.

RESULTS: Characteristic findings from magnetic resonance studies include variable T1W signal relative to skeletal muscle and hyperintense signal on fluid-sensitive imaging. Computed tomography has consistently demonstrated a sclerotic lesion with variable definition. Pathologic findings include sheets of multivacuolated cells with centrally placed nuclei and numerous tiny surrounding cytoplasmic vacuoles overlying bony trabeculae.

CONCLUSION: Our review of the literature demonstrates that intraosseous hibernoma is most likely an incidental finding with a predilection for the lower extremities in middle-aged females.

LEVEL OF EVIDENCE: 4.