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Int J Clin Exp Pathol 2013;6(10):2178-2184

Original Article
Deep-seated huge hibernoma of soft tissue: a rare differential diagnosis of atypical
lipomatous tumor/well differentiated liposarcoma

Nikolaos Vassos, Michael Lell, Werner Hohenberger, Roland S Croner, Abbas Agaimy

Department of Surgery, University Hospital, Erlangen, Germany; Institute of Interventional Radiology, University Hospital, Erlangen, Germany;
Institute of Pathology, University Hospital, Erlangen, Germany

Received July 24, 2013; Accepted August 21, 2013; Epub September 15, 2013; Published October 1, 2013

Abstract: Background: Hibernoma is a rare benign fat-forming soft tissue tumor that differentiates similar to brown fat, hence an origin from
remnants of fetal brown adipose tissue has been proposed. Mainly young adults are affected, usually without significant clinical symptoms.
Material and methods: We report on four patients with hibernomas, who were treated at our hospital during the last 10 years. The
clinicopathologic and immunohistochemical features are presented and treatment and follow-up data discussed. Results: Patients were 2
women and 2 men aged 21-67 years (mean: 45 yrs) who presented with a slowly growing, painless mass. The anatomic location was the
thigh, upper arm, lateral thoracic wall and paravertebral soft tissue. Two of them were diagnosed preoperatively through a percutaneous core
needle biopsy and the other two underwent surgery because of high clinical and radiological suspicion of liposarcoma. The tumor’s size
ranged from 7 cm to 15.5 cm (mean: 11 cm). All were deep-seated subfascial intramuscular masses. Histologically, all four tumors were of the
typical variant. All patients underwent a R0-surgical resection of the tumor and they were recurrence-free at last follow-up (mean: 47 months;
range: 25-87). Conclusion: Hibernoma may present as huge deep intramuscular soft tissue mass in adults, closely mimicking well
differentiated liposarcoma and should be considered in the differential diagnosis of fatty soft tissue tumors in any location. Surgical excision is
the treatment of choice. The tumor has no malignant or recurrence potential. (IJCEP1307043).

Keywords: Hibernoma, brown tissue, soft tissue tumor, deep-seated

Address correspondence to: Dr. Nikolaos Vassos, Department of Surgery, University Hospital Erlangen, Krankenhausstraße 12, 91054
Erlangen, Germany. Tel: +49-9131-85-33296; Fax: +49-9131-85-36294; E-mail: nikolaos.vassos@uk-erlangen.de