胸腺腫の頭蓋内転移―3例の報告

Intracranial Metastasis of Thymoma: Report of Three Cases

Ⅰ．はじめに

　胸腺腫は浸潤性に富む縦隔腫瘍である¹⁵⁾．その転移形態としては，局所浸潤の頻度が高く，主には肝臓，腎臓などの他臓器に転移するが，中枢神経系への転移は非常に稀である^2,3,4,13,19)．今回われわれは，3例の胸腺腫の頭蓋内転移を経験したので報告する．

　Thymoma with metastasis to the central nervous system is extremely rare. Herein,three rare cases of thymoma with intracranial metastasis are reported. Case 1 (thymoma,B3 in the WHO classification); cranial magnetic resonance imaging (MRI) revealed a mass lesion with a ring enhancement effect in the right temporal lobe. The cystic and hemorrhagic lesion was subtotally removed and radiation therapy of 40 Gy was administered to the tumor cavity containing the remains of the tumor around the ependyma. The patient received combination chemotherapy with carboplatin and gemcitabine hydrochloride,and he was discharged 3 months after the operation. Case 2 [(thymoma,C (thymic carcinoma)]; multiple cerebral metastases of 8 lesions were found and whole brain irradiation of 40 Gy was performed. Three months later,rapid development of 2 metastatic lesions resulted in the patient's death. At autopsy,neoplastic lesions were found in the neck lymph node,right shoulder,chest frame,pleural cavity,diaphragm,lung,periaortic lymph node,liver and pancreas. Case 3 (thymoma,B2); computed tomography (CT) scan and MRI showed a tumorous lesion over the cerebellar hemisphere. At operation,a vascular,elastic-soft and grey tumor was found to originate from the dura mater and had invaded the occipital bone. The tumor had also invaded the arachnoid membrane and sinus wall but the pia mater was free from invasion. Thereafter local irradiation of 40 Gy was performed to the tumor cavity containing the remains of the tumor around the sinus. However local recurrence reoccured 3 years later. After stereotactic irradiation of 40 Gy to the recurrent tumor,the tumor diminished. The patient is wheelchair-bound 3 years and 4 months after the operation.

　Most cerebral metastases are extremely rare. Outcome remains poor and life expectancy is very short when brain metastasis is present. Treatment for thymoma is multimodal,including surgery,irradiation and chemotherapy.