腫瘤内出血により進行性の症状を示した前頭骨内コレステリン肉芽腫の1例

Intratumoral Hemorrhage of Cholesterol Granuloma in the Frontal Bone Showing Rapid Progressive Symptoms: A Case Report

Ⅰ．はじめに

　コレステリン肉芽腫（cholesterol granuloma）はコレステリン結晶に対する生体防御反応により形成される肉芽腫である^6,15)．コレステリン結晶の発生機序として長期にわたる微小出血が考えられているが，大きな肉芽を形成した後にさらに出血し血腫形成による圧迫症状を呈することもありうる¹¹⁾．今回われわれは，前頭骨に発生し骨破壊・出血を伴い眼窩内へ圧迫を生じ，複視・眼瞼下垂で発見され，術前診断に苦慮したコレステリン肉芽腫の1例を経験したので報告する．

　A 30-year old man developed an exopthalmus in his right eye and diplopia at upward gaze those were progressive in two days. On admission, his upper eye lid in the right eye swelled and upward gaze was limited in the right eye. CT scan showed an osteolytic lesion in the right frontorbital bone. MR imaging showed a high signal tumor in both T1- and T2- weighted imaging with sharp margin and no enhancement. Right frontal craniotomy was performed and the cystic tumor consisting of old hematoma, and soft tissue surrounding the cyst was totally removed. The orbital roof had a large defect and tumor compressed periorbita. Neither communication with the frontal sinus nor mucosa with inflammation were seen. The postoperative course was uneventfull and pathological diagnosis was cholesterol granuloma with hematoma. Orbitofrontal bone is a rare site to have cholesterol granuloma. Most of them are asymptomatic. In our case, intratumoral hemorrhage caused compression on the perioribital, leading to a progressive mass sign. Preoperative differential diagnosis from other orbital tumors, such as epidermoid and lipoma was difficult.