再発を繰り返した巨大な仙骨部悪性末梢神経鞘腫瘍malignant peripheral nerve sheath tumorの1例

Giant Sacral Malignant Peripheral Nerve Sheath Tumor with Multiple Recurrence. Case Report

　再発を繰り返した巨大な仙骨部悪性末梢神経鞘腫瘍malignant peripheral nerve sheath tumor（MPNST）の1例を経験した．症例は26歳，女性．画像所見上で第5腰椎から仙骨前面の後腹膜腔に脊柱管内から連続する巨大な腫瘤を認め，神経鞘腫を疑い摘出術を行ったが，その後2年間で2回の再発を繰り返した．最終手術時の病理所見では腫瘍細胞の柵状配列は明らかでなく，S-100 protein陽性細胞が多い一方，MIB-1陽性細胞が多く認められたことから，低悪性度のMPNSTと考えられた．巨大な神経鞘腫ではこのような経過をとる症例もあるため，再発腫瘍に対する手術では可及的全摘を目指し，ときとして神経根切断も躊躇ってはならず，さらにその後の厳重な経過観察を要すると考えられた．

　We present a case report of a giant malignant peripheral nerve sheath tumor (MPNST). A 26-year-old woman with a giant tumor extending from the sacrum to the retroperitoneal space in magnetic resonance imaging (MRI) underwent surgery to have the tumor removed in a combined anterior and posterior approach. The initial diagnosis was benign schwanomma, based on histological findings, including a palisading pattern of tumor cells. The tumor recurred twice within two years after initial surgery, so she underwent revision surgery three times. In histological examination of the specimen from the last surgery, the palisading pattern had become unclear, while MIB-1-positive cells predominated. Based on both the clinical course and histological findings, the tumor was diagnosed as low-grade MPNST. She has had no recurrence or metastasis in the two and a half years since the last surgery. Patients with giant schwannoma should be followed up carefully, and, in recurrence, should be considered for malignant transformation.