頭部打撲を契機に増大をきたした頭蓋骨類上皮嚢胞の1症例

A Case of Enlargement of an Intradiploic Epidermoid Cyst by a Head Contusion

はじめに

　頭蓋骨に発生する類上皮嚢胞は稀な良性腫瘍であるが，頭蓋骨腫瘍の鑑別診断に加えなければならない疾患である^2）。本疾患は胎生期遺残産物から発生する腫瘍であり，稀な例として頭部外傷により皮膚組織が頭蓋骨板間層に残り腫瘍化するとされる^1，2）。

　この報告は，前額部類上皮嚢胞が同部の打撲を契機に増大したと推察された症例である。われわれが渉猟し得た範囲では，同腫瘍の増大機序に外傷が関連したとする報告はない。今回，その増大機序について以下に考察を加えていく。

Abstract

　We report a case of enlargement of a intradiploic epidermoid cyst following head trauma in a 19-year-old man.　The patient had a swelling on the right side of his forehead from the time of his birth.　He sustained a bruise in this region when he was 15 years old, following which the swelling gradually enlarged.　When the diameter of the mass increased to 5 cm, he visited our hospital.

　Computed tomography (CT) scan of the head showed a subcutaneous mass of low density extending from the diploe to the outer tables of the skull.　Magnetic resonance imaging (MRI) showed a hyperintense mass in both T₁- and T₂-weighted images.

　During the operation, we found a tumor that was intradiploic and had a thin capsule.　The effusion from the tumor resembled an old hematoma, and the tumor did not involve the paranasal sinuses.　We concluded the operation by performing cranioplasty using artificial bone.

　Histological examination revealed that the thin capsule consisted of stratified squamous epithelium and ciliated epithelium.　Needle-like cholesterol crystals and hemosiderosis were seen shown in the granulation-like tissue.　On the basis of these findings, we diagnosed the mass to bean intradiploic epidermoid cyst and thought that it might have grown following head trauma associated with chronic hemorrhage.　This paper reviews the differential diagnosis and pathologic findings of the intradiploic epidermoid cyst along with some previously published cases.

(Received: November 13,2008,Accepted: January 16,2009)