Pediatric Case With Rapidly Growing Hibernoma Due To Bleeding Into The Mass

Hibernomas are benign lesions developing from brown adipose tissue; they grow slowly and are very rare. They are mainly seen in adults and are localized on the scapulas, neck, axilla, thighs, intrathoracic and retroperitoneal fields. 13-year-old boy admitted to our clinic with the complaint of a painless mass that appeared on the left side of his neck two weeks ago. On his physical examination, there was a non-mobile, firm mass of 10 cm localized to the left supraclavicular area. In the superficial tissue ultrasonography of the affected area, the mass was evaluated as a hematoma; in color Doppler ultrasound, it did not show any relationship with arteries or veins. In magnetic resonance imaging, there was a 7x4 cm mass on left supraclavicular region between the skin and muscular tissues that appeared hyperintense on T1 and T2 weighted sequences. Following complete resection, histopathological examination was reported as typical variant hibernoma. The case is presented because of the rarity of hibernomas in children and the difficulty experienced in the diagnosis due to the bleeding into the mass lesion.