胃底腺型・胃底腺粘膜型腺癌と鑑別が必要な胃病変

Gastric Lesions Requiring Differential Diagnosis from Gastric Adenocarcinoma of the Fundic Gland and Fundic-gland Mucosa Types

要旨●胃底腺型腺癌は，胃底腺細胞への分化を示す胃型腫瘍で，粘膜固有層深部から膨張性に発育し，粘膜下層に浸潤して上皮下腫瘍（SEL）としての隆起を呈する．このうち，腺窩上皮細胞への分化を伴う腫瘍は胃底腺粘膜型腺癌と呼ばれ，内視鏡的には隆起型が主体だが，平坦型や陥凹型もみられる．両者とも上皮下に主座を置くため，生検による正確な診断が難しく，内視鏡所見の理解が診断の鍵となる．鑑別疾患としては，胃底腺型腺癌では上皮下に主座を置く腫瘍が，胃底腺粘膜型腺癌では表層に腺窩上皮型成分を伴う隆起型腫瘍が挙げられ，平坦・陥凹型では通常型の管状腺癌との鑑別が重要となる．

　Gastric adenocarcinoma of the fundic gland type（GA-FG）is a gastric-type tumor characterized by differentiation toward fundic gland cells. It typically exhibits expansive growth from the deep mucosa and invades the submucosa, presenting endoscopically as a subepithelial lesion. A subset of these tumors that shows differentiation toward foveolar epithelium is referred to as gastric adenocarcinoma of the fundic-gland mucosa type（GA-FGM）. While most GA-FGM lesions exhibit a protruded morphology, flat or depressed types also exist. Because GA-FG and GA-FGM are both primarily located beneath the surface epithelium, biopsy-based diagnosis can be challenging ; therefore, endoscopic recognition is critical for accurate diagnosis. The main differential diagnoses include other subepithelial tumors and protruded-type lesions with a foveolar epithelial component for GA-FG and GA-FGM, respectively. For flat or depressed-type GA-FGM, distinction from conventional well-differentiated tubular adenocarcinoma is essential.