若年者胃癌の特徴―中高年に認める胃癌との相違─病理の立場から

The Histological Characteristics of Gastric Cancer in the Young

要旨　まず進行癌を含めた30歳未満の若年者胃癌65例と，41歳以上の胃癌115例の臨床病理学的事項と癌周囲粘膜の慢性胃炎の程度，次に30歳未満の粘膜内胃癌18例（全例低分化腺癌）と41歳以上の低分化粘膜内胃癌42例の背景粘膜を比較した．背景粘膜はthe updated Sydney system guidelines（1994）に従い，組織学的に評価した．結果，若年者には，女性（69.2％ vs. 36.5％，p＜0.001），低分化腺癌（84.6％ vs. 65.2％，p＝0.004）が多かった．癌周囲粘膜の比較では，若年者のH. pylori感染率は高く（81.5％vs. 20.9％，p＜0.001），より多くの好中球浸潤を認め（p＝0.028），固有腺の萎縮や腸上皮化生の程度は軽かった（p＜0.001）．粘膜内胃癌の背景粘膜の比較では，体部のH. pylori菌体密度が若年者で有意に高く（p＝0.0012），体部，前庭部ともに腸上皮化生の程度は低かった（p＜0.01）．また，若年者の前庭部粘膜にリンパ濾胞過形成を認めた（p＝0.005）．以上から，若年者胃癌は，女性，低分化腺癌が多く，背景に腸上皮化生を伴わず，前庭部のリンパ濾胞過形成を示すH. pylori感染性胃炎（鳥肌胃炎）を伴うことが多いことがわかった．

　First, we compared 65 surgically resected specimens from young patients（below the age of 30 ; young group）and 115 surgically resected specimens of middle-aged or older patients（more than 40 years of age ; not-young group）with gastric cancer, including advanced cases. Moreover, histological findings of non-cancerous specimens around the cancer from the two groups were compared. 18 young cases with intramucosal gastric cancer of poorly-differentiated type and 42 not-young cases with tumors of the identical depth and histological type were observed and the degree of gastritis was compared, including H. pylori infection. The degree of gastritis and H. pylori infection was evaluated according to the updated Sydney system. In the young group, the prevalence among females（69.2％ vs. 36.5％, p＜0.001）and poorly differentiated adenocarcinoma（84.2％ vs. 65.2％, p＝0.004）were more frequently seen than in the not-young group. The incidence of H. pylori infection was significantly higher in the young group than in the not-young group（81.5％ vs. 20.9％, p＜0.001）. Within the surrounding non-cancerous mucosa, the density of neutrophilic infiltration was significantly more increased（p＝0.028）, and the degrees of glandular atrophy and intestinal metaplasia were significantly lower in the young group than in the not-young group（p＜0.001）. When we compared intramucosal gastric cancer in the young and the not-young patients, the incidence of H. pylori infection was significantly higher in the young group than in the not-young group（94.4％ vs. 35.7％, p＜0.001）, and the density of H. pylori was also higher in the body mucosa in the young group than in the not-young group（p＝0.0012）. Within the background mucosa, intestinal metaplasia in both body and antral mucosa was less frequent（p＜0.01）and antral lymphoid-follicle hyperplasia was more prominent（p＝0.005）in the young group than in the not-young group. Glandular atrophy was similar in both groups.

　In conclusion, poorly differentiated adenocarcinoma especially in females without intestinal metaplasia is more frequently seen in young patients with gastric cancer. Furthermore, intramucosal gastric adenocarcinoma of poorly differentiated type in young patients may be associated with H. pylori infection accompanied by antral chronic inflammation with lymphoid-follicle hyperplasia, regardless of the existence of intestinal metaplasia within the background gastric mucosa.