Large retroperitoneal hibernoma in an adult male: CT imaging findings with pathologic correlation.

Hibernoma is a rare benign tumor consisting primarily of brown fatty tissue. It is usually seen in locations where normal brown adipose tissue is found in fetuses and infants such as the periscapular or interscapular region, the neck, the axilla, the thorax, and, more rarely, the retroperitoneum. We report the computed tomographic findings and pathologic features of a large retroperitoneal hibernoma discovered in an adult male. Radiologists and surgeons should be aware that hibernoma should be included in the differential diagnosis of a large fatty retroperitoneal soft tissue tumor.