US AND CT FINDINGS OF HIBERNOMA IN AN UNUSUAL LOCATION

Purpose: Hibernomas are rare benign soft tissue tumors composed of brown fatty tissue. Retroperiotoneal localization is an unusual site for this tumor and only few cases of this entity have been published in the literature. The purpose of this presentation is to reveal the radiologic findings of this soft tissue tumor with histologic correlation.

Methods and Materials: A 13-year-old male was admitted to our clinic with 1 month history of periumblical abdominal pain, weight loss (6kg in 1 month) and sweating. There was no significant finding in physical examination. Abdominal X-Ray graphy, ultrasound(US) and abdominal-pelvic computarized tomography(CT) examinations were performed.

Results: There was no significant finding in plain abdominal radiography. Abdominal US revealed a 6×5 x3cm, well-circumferenced, hyperechoic, preaortic mass encasing celiac truncus, compressing aorta and splenic vein minimally. The proximal segment of superior mesenteric arter(SMA) was in close relation with the mass. Doppler US examination showed no stenotic finding in SMA or celiac artery. In CT and US there was no fatty plain between the mass and the pancreatic corpus. Be cause of the relationship with the main arterial vessels, the mass could not totally excited. Histologically, adiposits that belong to brown fatty tissue with centrally localized nucleus were seen and hibernoma was revealed as final diagnosis.

Conclusions: Hibernomas are asymptomatic, slow-growing tumors occuring in the anatomical sites where brown fatty tissue was found during fetal life such as inter-scapular region or thigh, retroperitoneal localization is exremelly rare. Although minority of retroperitoneal adipose tumors show histological signs of benignity, retroperitoneal hibernomas are benign in nature without evidence of metastasis or any signs of recurrence after surgery. Therefore hibernoma should be included in the differential diagnosis of retroperitoneal soft tissue tumors and total surgical excision is the remarkable choice for their treatment.