高齢者に発生したpilomyxoid astrocytomaの1例

Pilomyxoid Astrocytoma Presenting in an Elderly Patient:A Case Report

Ⅰ．はじめに

　Pilomyxoid astrocytoma（PMA）は近年提唱された比較的新しい脳腫瘍である．1985年のJanischら⁵⁾による‘diencephalic pilocytic astrocytoma with clinical onset in infancy’との報告が起源であり，PMAという名称は，1999年その病理組織所見に基づいてTihanらにより提唱された¹²⁾．2000年のWHO分類ではpilocytic astrocytoma（PA）の亜型とされていたが，臨床像・組織像ともにPAとは異なるため，2007年の改訂で新しいICD-O（international classification of diseases for oncology）codeを有するglioma sectionの腫瘍として分類された^1,8)．一般的には乳幼児期に発症するが，最近では成人例も報告されている^2,3,4,7)．われわれは高齢者に発症したPMAを経験したので報告する．

　A 77-year-old man presented with progressive visual disturbance. MR images revealed a mass lesion mainly spreading in the left basal cistern, sylvian fissure and to the left hypothalamic region, with ventricular enlargement. To obtain precise diagnosis of the mass lesion, an open biopsy was performed. The pathological diagnosis was pilomyxoid astrocytoma (PMA). The patient was discharged without adjuvant therapy. A Ventriculoperitoneal shunt procedure was performed afterwards because his hydrocephalic symptoms progressed.

　PMA is a rare tumor newly added to the glioma section by the WHO classification renewed in 2007,and generally develops in infancy. To our knowledge,there are only four adult cases being reported. In those cases,the symptoms of the disease developed during the second to fourth decade of life. The onset at a more advanced age as in the present case seems to be extremely rare. The treatment strategy described in infant cases is similar to that for pilocytic astrocytoma,but there are only few reports. To establish a treatment protocol for adult patients,further more cases are needed to accumulate knowledge of this rare brain tumor.