Incidental lipoma-like hibernoma arising from the adrenal gland: a well-differentiated liposarcoma mimicker.

[well-differentiated liposarcoma]

Hibernomas are uncommon benign lipomatous tumors which show differentiation toward brown fat . To our knowledge , only one case of adrenal hibernoma has been previously reported . We describe a 55 -year -old woman showing an incidental , 1 .7 cm -hibernoma associated with a 2 .6 cm -cortical adenoma producing primary hyperaldosteronism (Conn 's syndrome ), both in the left adrenal gland . The hibernoma was composed predominantly of univacuolated mature fat cells admixed with small vessels . Scattered areas composed of large multivacuolated pale cells with central or paracentral nuclei , mimicking lipoblasts , accounting for less than 30 % of the tumor , were found . These cells lacked nuclear hyperchromasia or marked atypia , were S 100 -positive , and showed numerous mitochondria reactive with the anti-mitochondrial antibody . A diagnosis of lipoma -like hibernoma was made . Pathologists should be aware of this variant of hibernoma to avoid misdiagnosis and excessive treatment .