著明な囊胞を伴った頸椎monostotic fibrous dysplasiaの1例

A Case of Cervical Monostotic Fibrous Dysplasia with a Large Cyst

Ⅰ．はじめに

　線維性骨異形成fibrous dysplasia（以下FD）はLichtensteinが1938年に初めて報告しており，未熟な骨組織と線維性組織からなる非腫瘍性骨病変で小児に多く，顎，肋骨，大腿骨，脛骨などの長幹骨骨端部に好発すると言われている^1,13)．また，1つの骨に限局する単骨性（monostotic）と多数の骨に発生する多骨性（polyostotic）に区別される．その中で，脊椎，特に頸椎に発生するFDは比較的稀であり，さらに単骨性のものは報告上少なく，画像所見上巨細胞腫giant cell tumor等との鑑別が問題となり，診断的意義も含めて外科的に摘出術が必要となることが多い．

　今回，第2頸椎に発生した単骨性で，退形成性変化と考えられた著明な囊胞を伴っていた症例を経験したので，文献的考察を加えて報告する．

　We report a rare cervical monostotic fibrous dysplasia with a large cyst in the C2 region in a 55-year-old man complaining of headache. MRI revealed an expanding bony tumor at the C2 spinous process. Gd-DTPA MRI showed slight enhancement around a cystic mass. We performed C2 laminectomy and removed the tumor. It was comprised of soft tissue in the C2 spinous process and right lamina and contained a large septated cyst filled with xanthochromic fluid. Histopathology confirmed fibrous dysplasia with typical woven bony trabeculae. His postoperative course was uneventful and outpatient follow-up detected no deficits.

　Cervical fibrous dysplasia with a distinct cyst is a rare entity and few cases have been reported in the literature. Such cysts are considered to reflect a tumor regression process. Diagnosis based on MRI and CT study alone is difficult. We suggest that these lesions be surgically resected.