スキルス胃癌の特徴と診断の基本―病理の立場から

The Histological Features of the Scirrhous Gastric Carcinoma

要旨　びまん浸潤型胃癌，いわゆる4型スキルス胃癌を，粘膜内成分の癌組織型に着目して背景粘膜および癌進展形式を検討した．対象は，術前治療を施行されていない胃切除例161例で，粘膜内成分に腺管形成のない純粋低分化型（pure type，n＝98）と腺管形成のある腺管混合型（mixed type，n＝63）に分けて比較した．純粋低分化型の粘膜内病変は，胃体部に有意に多く（p＜0.001），胃壁内に線維性組織の著しい増生を伴い孤立散在性に浸潤していた．一方，腺管混合型の粘膜内病変は幽門前庭部に多く，浸潤部でも腺管形成能は保たれ（36.5％/2.0％，p＜0.001），リンパ管侵襲が著明でリンパ節転移も高率に認めた（p＜0.001）．背景粘膜の萎縮や腸上皮化生の程度は，純粋低分化型で有意に軽かった（p＜0.001，p＝0.01）．以上から，組織学的にスキルス胃癌には，萎縮や腸上皮化生が軽い胃底腺領域に発生した低分化型腺癌が増生した線維性間質の中に孤立散在性に浸潤するものと，体下部～幽門前庭部から発生した分化型腺癌が浸潤するにつれて低分化になり，高率にリンパ管浸襲，リンパ節転移を認めるものの，2つの異なるタイプが存在することが示された．

　On the basis of difference in histological features of the intramucosal component, we investigated the background mucosa and invasive pattern of scirrhous gastric carcinoma. We chose 161 cases of diffusely infiltrating gastric carcinoma, which were surgically resected without preoperative therapy. Then, we compared 98 cases of ‘pure type’, showing poorly differentiated adenocarcinoma of both the intramucosal and invasive area without any glandular component, with 63 cases of ‘mixed type’, showing the coexistence of poorly differentiated adenocarcinoma and intramucosal glandular component. In the cases of the pure type, the intramucosal predominant area was located significantly in the body of the stomach（p＜0.001）, and carcinoma cells had infiltrated diffusely and were, accompanied by abundant fibrosis through the gastric wall. In the cases of mixed type, the intramucosal predominant area was located in the antrum of the stomach, and the glandular component persisted in the invasive area（36.5％/2.0％, p＜0.001）. Glandular atrophy（p＝0.01）, and intestinal metaplasia（p＜0.001）in the background mucosa, prominent lymphatic permeation（p＜0.001）and lymph node metastasis（p＜0.001）were more frequently observed in the mixed type than the pure type. As indicated above, there seem to be 2 histological subtypes of scirrhous gastric carcinoma ; one has the nature of poorly differentiated adenocarcinoma, arising in the body mucosa with less glandular atrophy and intestinal metaplasia and infiltrating with abundant fibrosis. The other is differentiated adenocarcinoma arising in the antral mucosa, changed into poorly differentiated adenocarcinoma in the invasive area with prominent lymphatic permeation and frequent lymph node metastasis.