Imaging Characteristics of Hibernomas

Purpose: To report a single-center experience with imaging hibernomas

Materials and Methods: We present three cases of indeterminate fatty masses that were pathology proven to be hibernomas, one of which was subsequently embolized.

Results: Case 1: A 53-year-old female patient with follicular thyroid carcinoma, now found to have a right posterior thigh mass. An ultrasound-guided biopsy was first performed. Ultrasound completed during the biopsy demonstrated a hyperechoic mass. Magnetic resonance imaging (MRI) was subsequently performed and demonstrated a heterogeneous T1 hyperintense mass with signal drop out on fat-supposed images. Case 2: A 53-year-old male patient with no history of malignancy was incidentally found to have a sclerotic left iliac bone lesion on an MRI completed for back pain. On MRI, T1-weighted images demonstrated a hypointense well-circumscribed lesion in the left iliac wing. T2-weighted images demonstrated the lesion to be hyperintense without surrounding edema. A computed tomography (CT) scan demonstrated a well-circumscribed hypoattenuating lesion with a sclerotic border. A nuclear medicine three-phase bone scan demonstrated increased blood flow to the lesion. The patient subsequently underwent a CT-guided bone biopsy, for which pathology came back as a hibernoma. Case 3: A 56-year-old male patient with left hip pain caused by a left sciatic notch hibernoma, for which embolization was requested. A left common iliac arteriogram was first performed, which demonstrated that the external iliac did not perfuse the hibernoma. Selective arteriogram of the posterior branch of the internal iliac demonstrated increased vascularity proximally, with numerous arteries arising from the superior gluteal artery. Embolization of several proximal superior gluteal artery branches was performed with 350- to 500-μm Embospheres. The final arteriogram demonstrated decreased vascularity to the mass. After the procedure, the patient did endorse increased left hip pain with numbness, but it resolved with a methylprednisolone taper.

Conclusions: Hibernomas are rare entities that can mimic lipomas or liposarcomas. If there are unusual imaging characteristics, such as increased vascularity, increased fluorodeoxyglucose uptake on positron emission tomography/computed tomography, or retroperitoneal in location, biopsy may be indicated to differentiate a hibernoma from malignancy. In this case series, we have presented the different imaging characteristics of hibernomas.