スキルス胃癌の特徴と診断の基本―X線の立場から

Basis of the Diagnosis and Feature of Scirrhous Gastric Cancer

要旨　“スキルス胃癌”のX線診断について，胃壁の伸展状況の違いから症例を提示して概説した．スキルス胃癌はびまん性に広範囲で粘膜下組織を浸潤し，線維性組織増生を伴い胃壁の硬化と収縮，管腔の狭小化を示す．その特徴的なX線所見は，概観像では管腔の狭小化をはじめ辺縁の硬化や伸展不良，不整な彎入で，ひだの所見は肥大や横径の不同，屈曲・蛇行，間隙の辺縁不整などを示す．一方で，スキルス胃癌のうちLP型胃癌の中には“伸展が保たれている”症例が存在し，そのX線所見は典型的な変形や伸展不良，ひだ走行の変化があらわれにくく，浸潤領域内においても限局した部位でのみ所見が得られることがある．その際には浸潤を来した領域の粘膜に着目し，不規則な胃小区様模様や顆粒陰影，ひび割れ様所見などのわずかな粘膜像の所見を有するので撮影と読影には注意を要する．胃底腺領域のIIc様病変を認めた際には，LP型胃癌を念頭に置いて，撮影では空気による胃壁の伸展を調節し，バリウムの移動を利用してはじきやたまりからわずかな伸展不良や硬化像の有無を明らかにし，診断においては軽微な粘膜所見をとらえてゆくことが重要である．

　We present cases of scirrhous gastric cancer to describe diagnostic evaluation of gastric wall distention demonstrated by upper GI series. Scirrhous cancer shows diffuse invasion of a broad range of submucosal tissues, and the consequent increase in fibrotic tissue leads to gastric wall induration, contraction, and stenosis. The characteristic features on upper GI series are luminal stenosis, marginal induration, poor extension, irregular curvature, and swollen, serpiginous, and curving folds with various transverse diameter or inconstant edges of space between folds. On the other hand, some cases with LP（linitis plastica）type scirrhous cancer show good extension and do not show the typical deformity, poor distension, or irregular folds on upper GI series, but only focal alterations even in the infiltrated area. Accurate observation of detailed mucosal findings is essential in the invaded area, such as unordered gastric small segment-like, granular shadow, or cracked-like structures.

　In cases with type IIc in the gastric fundic area, gastric wall distension should be modulated by controlling air inflation during x-ray study, attempting to depict subtle abnormal distension or duration, or pooling or of defective barium contrast, to interpret these mucosal manifestations.