Huge hibernoma of the neck with extension into the mediastinum

Hibernomas are benign tumors made up of brown fat. They are rarely encountered in otolaryngologic clinical practice, as they are usually located in the interscapular area, axilla, thigh, mediastinum, and retroperitoneum. We report an extremely rare case of a very large hibernoma in a 45-year-old man who presented with a 4-year history of neck swelling. Radioimaging was suggestive of a mass in both parapharyngeal spaces; the lesion was more prominent on the left side. The mass extended from C2 into the retropharyngeal space and superior mediastinum. Fine-needle aspiration cytology failed to yield a diagnosis. On surgical exploration, a tumor measuring 17 × 16 × 5 cm was removed and sent for histopathologic examination. Light microscopy was suggestive of a hibernoma. Staining with oil red O confirmed the diagnosis. To the best of our knowledge, a large hibernoma with such massive extension has not been previously reported in the literature.