Hibernoma of the Thigh: A Report of Four Cases

Abstract

Hibernoma is a rare benign adypocyte tumour of brown fat. We report on 4 patients with hibernoma of the thigh. Clinical features and magnetic resonance imaging suggested the tumours were liposarcomas, but biopsy yielded the diagnosis of hibernoma. All 4 patients underwent complete excision of the tumour and had no recurrence.

An unusual presentation of a rare benign tumor in the head and neck: A review of hibernomas

“…A CT scan distinguishes the density of the hibernoma from that of muscle and fat. Further enhancing the image by adding contrast highlights the hypervascular nature of these tumors . Hibernomas tend to be larger than 10 cm at the time of diagnosis, and may compress adjacent anatomical structures…”

“…Nonlipoma subtypes tend to be heterogeneous, hypo‐ or isointense on MRI, with hypervascularity, and may interfere with identification of a hibernoma . Suppressing fat on MRI with intense gadolinium enhancement, particularly in areas of low signal, may identify any vasculature present in a hibernoma . However, even MRI has limitations.…”

“…However, adults can have metabolically active brown fat independent of a hibernoma, and accordingly, PET has little value as a diagnostic tool. Finally, on ultrasound, a hibernoma will appear uniformly hyperechogenic, its angiography showing increased vascularity and occasional arteriovenous shunts …”

“…Macroscopically, hibernomas appear well‐demarcated and soft, are contained within thin capsules, and range in color from light brown to gray . Hibernomas contain large multivacuolated cells with abundant mature adipocytes, small capillaries, round cells, a central pit, and eosinophilic cytoplasm representing brown fat cells . There are generally four histological variants of hibernoma: typical, spindle, lipoma‐like, and myxoid .…”

“…Immunohistochemical positive staining with S‐100 and oil red O‐positive droplets of cytoplasmic lipid can been seen in most hibernomas, with negative CD34 markers more commonly seen as positive in spindle cell or other lipid containing tumors . Interestingly, the cytogenetics of hibernomas may reveal chromosome abnormalities such as reciprocal translocation of 9q34 and 11q13 bands …”