胃癌類似形態を呈した胃限局性ATTRアミロイドーシスの1例

Localized Transthyretin-Associated Gastric Amyloidosis Mimicking Gastric Cancer, Report of a Case

要旨　患者は70歳代，女性．心窩部痛を主訴に受診した近医の上部消化管内視鏡検査で胃に異常を指摘されたため，当科へ紹介され，受診となった．胃体下部大彎前壁寄りに発赤した大小不揃いの結節状隆起を認めた．粘膜下腫瘍様病変を呈し，粘液の付着を認めたために粘液癌が疑われたが，生検でアミロイドーシスと診断された．さらに，免疫染色にてTTR（transthyretin）陽性であることから，ATTRアミロイドーシスと診断された．TTRの遺伝子変異はなく，野生型TTR由来の老人性アミロイドーシス（senile systemic amyloidosis ; SSA）と最終的に診断した．他の消化管，他臓器にアミロイドの沈着を認めず，胃に限局されたATTRアミロイドーシスの1例であった．SSAも消化管アミロイドーシスを合併しやすく，アミロイドーシスの分類にはTTRを含めた免疫染色で行うべきである．

　An elderly woman in her seventies was admitted with epigastric pain. An upper gastrointestinal endoscopy revealed a tumor-like lesion at the inferior part of the gastric corpus ; the lesion was elevated with surrounding erythema. Gastric cancer was suspected considering the finding of the submucosal tumor.

　Histological examination of biopsy specimens from the lesion showed a deposition of amorphous, homogeneous, and acidophilic material in the gastric mucosa. This was consistent with a diagnosis of gastric amyloidosis.

　Immunohistochemistry for ATTR（amyloidogenic transthyretin） was strongly positive. There was no gene mutation of TTR ; and it carried out the final diagnosis to the ATTR of wild type TTR（senile systemic amyloidosis ; SSA）. This was a rare case of localized gastric amyloidosis of ATTR. SSA also easy to merge the digestive tract amyloidosis. The classification of amyloidosis should be made based on immune staining including TTR.