title: Deep-seated huge hibernoma of soft tissue: a rare differential diagnosis of atypical lipomatous tumor/well differentiated liposarcoma.
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.
  
  
  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).
  
  
  CONCLUSIONS
  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.
authors.affiliation: Department of Surgery, University Hospital Erlangen, Germany.
authors.forename: Nikolaos
authors.initials: N
authors.lastname: Vassos
authors.forename: Michael
authors.initials: M
authors.lastname: Lell
authors.forename: Werner
authors.initials: W
authors.lastname: Hohenberger
authors.forename: Roland S
authors.initials: RS
authors.lastname: Croner
authors.forename: Abbas
authors.initials: A
authors.lastname: Agaimy
mesh_terms: D000328:Adult; D000368:Aged; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D008067:Lipoma / Q000473:pathology*; D008080:Liposarcoma / Q000473:pathology*; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D012983:Soft Tissue Neoplasms / Q000473:pathology*
keywords: Hibernoma; brown tissue; deep-seated; soft tissue tumor