Helicobacter pylori陰性の胃底腺粘膜関連腫瘍―胃底腺型胃癌と胃底腺ポリープの腫瘍化

Two Types of Neoplasia in Fundic-Gland Mucosa without Helicobacter pylori Infection : Gastric Carcinoma and Polyp with Dysplasia

要旨　胃底腺型胃癌は，Helicobacter pylori（H. pylori）と関連のない胃癌であり，低悪性度で予後良好な腫瘍と考えられていたが，高悪性度の病変も存在することが判明してきた．その発生および発育進展過程において，Wntシグナル系の活性化の関連やGNAS遺伝子変異との関連が示唆されているが，臨床的取り扱いに有用となる悪性度に関連した細胞学的および分子生物学的因子の解明が今後の課題である．胃底腺ポリープもH. pyloriと関連のない病変で，悪性の危険性はない病変とされていた．しかし，近年散発性のものでもβカテニンの遺伝子異常を認めることから腫瘍性である可能性が示唆され，まれではあるが腫瘍化した症例も報告されている．今後，H. pylori感染率が低下している中で，これら胃底腺粘膜関連病変に対して新たな視点をもって注目する必要がある．

　There is a type of gastric carcinoma of the fundic gland that is not associated with Helicobacter pylori（H. pylori）infection. This gastric carcinoma is believed to be a low-grade tumor with favorable prognosis, but there are reports of high-grade tumors. A mutation in the GNAS gene and activation of the Wnt signaling pathway are possibly associated with the development and progression of such tumors. Further research is needed to elucidate the cytological and molecular factors related to the biological behavior, which may predict the response to treatment. A FGP（fundic gland polyp）is not associated with H. pylori infection either and is believed to carry no risk of malignancy. Recently, FGP is suggested to become neoplastic due to a β-catenin gene mutation even in sporadic cases. FGPs with neoplastic transformation have also been reported. In the future, the H. pylori infection rate will be decreasing ; thus, it is necessary to draw more attention to the new risks of these 2 types of lesions in the fundic gland mucosa.