Unusual 'dumbbell'-shaped hibernoma

Abstract

Hibernoma is considered as a rare soft tissue benign tumor originating from brown fat. Few cases have been described so far in the literature; hibernoma was first described by Merkel in 1906, but it was named by Gery in 1914. We present the case of 33-year-old woman who presented with a palpable lump over superior aspect of her thigh associated with pain. Magnetic resonance imaging examination reported a "dumbbell"-shaped soft tissue tumor involving the right side of the pelvis and adductor compartment passing through the obturator foramen into the adductor compartment infiltrating the hip joint. Clinical and imaging features initially suggested liposarcoma, but ultrasound-guided biopsy and final surgical resection yielded the diagnosis of hibernoma. This rare soft tissue tumor can imitate malignancy, but magnetic resonance imaging and possibly guided biopsy are essential for preoperative planning as surgical resection remains the best management pathway.