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Neurological Surgery No Shinkei Geka Volume 43, Issue 9 （September 2015）

Neurological Surgery 脳神経外科 43巻9号（2015年9月発行）

Japanese English

症例

Pilomyxoid-spectrum astrocytoma 2例の臨床病理学的検討—BRAF遺伝子異常の検討も加えて Clinicopathological Study of Pilomyxoid-Spectrum Astrocytomas:An Analysis of the BRAF Gene. Report of Two Cases 伊東民雄 ¹ , 佐藤憲市 ¹ , 及川光照 ¹ , 杉尾啓徳 ¹ , 浅野目卓 ¹ , 尾崎義丸 ¹ , 中村博彦 ¹ , 田中伸哉 ² , 津田真寿美 ² , 長嶋和郎 ³ Tamio ITO ¹ , Kenichi SATO ¹ , Mitsuteru OIKAWA ¹ , Hironori SUGIO ¹ , Taku ASANOME ¹ , Yoshimaru OZAKI ¹ , Hirohiko NAKAMURA ¹ , Shinya TANAKA ² , Masumi TSUDA ² , Kazuo NAGASHIMA ³ ¹中村記念病院脳神経外科，脳腫瘍センター ²北海道大学大学院医学研究科腫瘍病理学分野 ³札幌東徳洲会病院病理診断科 ¹Department of Neurosurgery, Brain Tumor Center, Nakamura Memorial Hospital ²Department of Cancer Pathology, Hokkaido University Graduate School of Medicine ³Department of Pathology, Sapporo Higashi Tokushukai Hospital キーワード： pilocytic astrocytoma , pilomyxoid astrocytoma , intermediate pilomyxoid tumor , clinicopathological study , BRAF Keyword: pilocytic astrocytoma , pilomyxoid astrocytoma , intermediate pilomyxoid tumor , clinicopathological study , BRAF pp.825-833

発行日 2015年9月10日 Published Date 2015/9/10

DOI https://doi.org/10.11477/mf.1436203129

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Abstract 文献概要
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Ⅰ．はじめに

　Pilomyxoid astrocytoma（PMA）はbiphasic patternをとるpilocytic astrocytoma（PA）とは異なり，背景はmonophasicなmyxoid patternをとる腫瘍として1999年にTihanらにより提唱された¹⁹⁾．2007年のWHO脳腫瘍分類では，PMAはPAと比べて乳幼児に発生し予後も悪いことからGrade Ⅱとして分類されている¹⁷⁾．しかしながらPMAは再発時にPAにmatureしたという報告が散見され^1,12)，2010年にJohnsonらは両者は一連のspectrum上にあるとして“intermediate pilomyxoid tumors（IPTs）”の概念を提唱している¹²⁾．

　一方，PAではBRAF遺伝子異常（KIAA1549-BRAF fusion）が約70%にみられるが^{3,4,7,8,11,15)}，PMAでの報告は少ない．今回われわれはPMAおよびIPT，すなわちpilomyxoid-spectrum astrocytoma（PMSA）と考えられた2例を経験したので，その臨床病理像をBRAF遺伝子異常の検討も加え報告する．

　In contrast to pilocytic astrocytomas（PAs), pilomyxoid astrocytomas（PMAs）demonstrate monophasic piloid cells with angiocentric distribution and a more aggressive clinical course. Recently, several reports have described combined histological features of both subtypes;accordingly, these were termed intermediate pilomyxoid tumors（IPTs). The KIAA1549-BRAF fusion gene has been found in approximately 70% of PAs, but is reportedly rare in PMAs. We describe a clinicopathological study of two patients with pilomyxoid-spectrum astrocytoma（PMSA). Case 1 was of a 29-year-old man who presented with a generalized seizure. Gadolinium-magnetic resonance imaging（Gd-MRI）demonstrated a less enhanced tumor in the left temporal lobe. Case 2 was of a 9-year-old boy who presented with headache. Gd-MRI revealed an irregularly enhanced tumor in the left cerebellum. In Case 1, the tumor showed monomorphous bipolar cells in a myxoid background and angiocentric arrangement;therefore, the diagnosis was PMA. In Case 2, part of the tumor had a myxoid, angiocentric pattern characteristic of PMA;the other part had a biphasic pattern characteristic of PA. PMA and PA were mixed in a 7:3 ratio;therefore, IPT was diagnosed. No BRAF V600E mutations were found by immunohistochemistry and sequencing in either case. Three major KIAA1549-BRAF fusion subtypes were analyzed by quantitative reverse transcription polymerase chain reaction（RT-PCR）and sequencing. No fusions were found in Case 1. However, K16-B9 fusion was identified in Case 2, and this fusion was more prevalent in the PA component than in the PMA component. In summary, no BRAF V600E mutations were found in PMSAs, but KIAA1549-BRAF fusion was identified in IPT, particularly in the PA component.