上位頚髄に発生した放射線関連malignant peripheral nerve sheath tumor（MPNST）の1例

Radiation-Induced Malignant Peripheral Nerve Sheath Tumor of the High Cervical Spine

Ⅰ．はじめに

　Malignant peripheral nerve sheath tumor（MPNST）は稀な軟部組織悪性腫瘍である．疫学的には軟部組織の悪性腫瘍の5%，末梢神経系腫瘍の0.4%を占める．30〜60代が好発年齢とされ，やや男性に多い．半数以上はneurofibromatosis-1（NF1）に合併するが，孤発例（sporadic）¹¹⁾も報告されている．四肢の末梢神経に好発し，脊髄に原発するものは比較的稀である^{2-5,7,8,10,11)}．

　今回われわれは，放射線治療後17年の経過で良性のschwannomaから悪性転化を来したと考えられた脊髄MPNSTの1例を経験したので文献的考察を含め報告する．

　Case:A 30-year-old woman presented with posterior cervical pain and left-sided omalgia. The patient had a history of non-Hodgkin's lymphoma for which she had received prophylactic whole-brain irradiation（including at the upper cervical level）17 years previously. A magnetic resonance imaging（MRI）scan obtained 1 month previously showed an intradural extramedullary mass lesion at the left C1/2 level. We initially considered the tumor to be a benign schwannoma, but the patient subsequently developed left hemiparesis and was consequently admitted 2 days after her first visit. A second MRI scan showed that the tumor had progressed markedly. Hence, the patient underwent emergency surgical excision of the tumor. However, the tumor could only be partially removed because it had strongly adhered to the ventral aspect of the spinal cord. The tumor was pathologically diagnosed as a malignant peripheral nerve sheath tumor（MPNST). The residual tumor was subjected to local irradiation and surgery, but the treatment was unsuccessful, and the patient died on the 91st day of her illness.

　Conclusion:We report a case of radiation-induced high cervical MPNST arising from a benign schwannoma. All 9 previously reported cases of radiation-induced spinal MPNST were reviewed. Intraspinal MPNST of the high cervical region are extremely rare and are associated with a very poor prognosis. The 5-year survival rate of such tumors is markedly worse than that of other types of MPNST, and no standard treatment has been established for this condition.