スキルス胃癌のX線診断—4型胃癌の年次推移，形態学的・病理組織学的検討

X-ray Diagnosis for Scirrhous Gastric Cancer

要旨●スキルスとは，病理組織学的に癌組織の間質に線維性組織増生が顕著な状態の総称であり，スキルス胃癌は臨床的に「胃癌取扱い規約」の肉眼型の4型を指すことが多い．そこで，本邦における4型胃癌の経時的な発生頻度，形態学的・病理組織学的特徴を検討した．全国集計による進行胃癌の肉眼型別・年次推移をみると，4型胃癌は，1984年度13.8%から2014年度6.5%に減少していた．また，当センターにおいて過去29年間に経験した4型胃癌93例を対象として，原発巣（粘膜内進展部）の部位と背景粘膜から，①胃底腺型，②腺境界型，③幽門腺型の3型に分類し，2007年度を境に前期45例，後期48例に分けて検討した．後期では胃底腺型が特に減少し，腺境界型，幽門腺型の割合が増加していた．胃底腺型は，前後期ともに原発巣の大きさが25cm²以下で陥凹は深く組織型は未分化型腺癌が多かった．一方，腺境界型は，前後期ともに原発巣の大きさが50cm²以上で陥凹は浅かったが，後期では組織混在型の割合が増加していた．幽門腺型は原発巣の大きさに比較して粘膜下層以深の面積は大きくなく，前後期ともに組織混在型が約30%に認められた．H. pylori感染状態の検討では，前期はすべて現感染であったが，後期では現感染42例，未感染2例（胃底腺型2例），除菌後4例（胃底腺型1例，腺境界型2例，幽門腺型1例）であった．以上から，スキルス胃癌，4型進行胃癌の正確な診断のためには，原発巣の部位・背景粘膜の相違による形態学的・病理組織学的特徴を十分に理解して，スクリーニング，精密検査を行うことが重要である．

　In this study, we divided type 4 advanced gastric cancer into three broad types on the basis of the primary tumor site, namely, “fundic gland”, “borderline zone of the fundic gland”, and “antral gland” types, and investigated their clinicopathological characteristics over time. The incidence of type 4 advanced gastric cancer in Japan decreased from 13.8% in 1984 to 6.5% in 2014. In our hospital, 93 patients were diagnosed with this cancer in the past 29 years ; they were divided into two groups based on their date of diagnosis（pre- and post-2008）to examine the differences in the incidence of each type of cancer in the two groups. Our results showed that the fundic gland type decreased, whereas the borderline zone of the fundic gland and antral gland types increased in the later phase compared with the former phase. In the fundic gland type, the primary lesions were ≦25mm in size, deeply depressed, and histologically classified as undifferentiated adenocarcinoma in both pre- and post-2008 groups. In contrast, in the borderline zone of the fundic gland type, the primary lesions were ≧50mm in size and shallowly depressed, and the incidence of mixed histological types increased in the later phase. Results of infection tests for H. pylori（Helicobacter pylori）showed that all 45 patients in the former phase were infected with H. pylori. In the latter phase, 42 patients were infected with H. pylori, 2 were uninfected, and 4 had H. pylori eradicated. All the uninfected cases had the fundic gland cancer type with the primary lesions located in the cardia（one patient）and lesser curvature of lower gastric body（one patient）. In the eradicated cases, the cancer types were：fundic gland（one patient）, borderline zone of the fundic gland（two patients）, and antral gland（one patient）.