Hibernoma: A Rare Benign Tumor

Hibernomas are rare soft-tissue benign neoplasms composed of brown adipose tissue. In 1906, Merkel named these tumors Pseudolipoma, then in 1914, Grey coined the term as Hibernoma because of its similarity to brown fat in hibernating animal species. Symptoms secondary to extrinsic compression of neighboring structures may be present, although these tumors are uniformly benign. Hibernomas may be found anywhere in normal fetal brown fat but are most commonly located in the thigh. The etiology of Hibernomas is unknown. Molecular genetics show mutation in chromosome 11 which encodes the tumor suppressor gene MEN 1 [Multiple Endocrine Neoplasia type 1]. Among all benign lipomatous tumors approximately 1.6% accounts for Hibernomas.