大腰筋内に発生した神経鞘腫の1例

Schwannoma Developing in the Psoas Major Muscle: A Case Report

Ⅰ．はじめに

　神経鞘腫は，末梢神経のSchwann細胞に由来する腫瘍で，末梢神経の存在する部位に発生し得る．今回われわれは，腰椎脊柱管外である大腰筋内に発生した稀な神経鞘腫に対し外科的治療を行い良好な治療成績を収めたので，文献的考察を含めて報告する．

　Schwannoma can occur wherever peripheral nerve Schwann cells are found. However, retroperitoneal schwannoma is extremely rare in that only 16 cases have been reported, including that of the present patient. A 51-year-old male complained of chronic lower back pain and paresthesia in the lower left region. Lower back pain increased with leftward bending. Magnetic resonance imaging (MRI) revealed a neoplastic lesion about 6 cm in diameter in the left psoas major muscle, and the lesion was in contact with the L4 and L5 vertebral bodies. The tumor did not continue to the lumbar foramen. The symptom had become disabling, therefore tumor removal was performed using Wiltse’s approach. From intraoperative findings, the origin of the tumor was suspected to be the L4 nerve root. The ventral surface of the tumor could not be observed with this posterior approach. Lumbar plexus might adhere closely to the ventral surface of the tumor, therefore the capsule of the tumor was left to avoid neurological deterioration. Schwannoma was diagnosed by pathological analysis, and no malignancy was evident. After the operation, symptoms were completely relieved, and the residual capsule of the tumor diminished in size on MRI after 12 months. The posterior Wiltse's approach can be useful to treat mass lesions in the psoas major muscle. The 16 reported cases of retroperitoneal schwannoma, including that of the present patient, are reviewed.