頰骨弓下に発生した多形型脂肪肉腫の1症例

A case of pleomorphic liposarcoma arising under the zygomatic arch

はじめに

　わが国における骨軟部悪性腫瘍の発生率は10万人に2人で，剖検数からみた全悪性腫瘍に占める頻度は0.14％である^1）。そのうち，脂肪肉腫の発生頻度は38.4％と最も高い^2）。しかし，頭頸部における発生は全肉腫中の1.0～2.4％と稀であり^2～5），全脂肪肉腫中の1.5～4.4％と報告されている^4,6,7）。頭頸部の発生部位では頸部が最も多く，頰部の発生はきわめて稀である^3,6）。

　今回われわれは，20代男性の右頰骨弓下に発生した多形型脂肪肉腫（pleomorphic liposarcoma：PLS）の1症例を経験したので，若干の考察を加えて報告する。

　A 27-year-old man presented with a non-tender swelling of his right cheek several days after a strong contusion. CT and MRI findings revealed that the lesion was a well-demarcated mass localized under the zygomatic arch with a partial invasion. He underwent a total removal of the tumor using the coronal incision. The histopathological diagnosis was pleomorphic liposarcoma which is defined morphologically by the presence of pleomorphic lipoblasts, accounting for approximately 5％ of liposarcoma and clinically behaves as a high-grade sarcoma.

　There had been no recurrence at the 13-years point postoperatively, however close follow-up should be still mandatory.