臨牀消化器内科 Vol.13 No.6(2-1)


特集名 消化器の前癌病変
題名 胃の前癌病変 (1) ポリープ(adenoma)
発刊年月 1998年 06月
著者 吉田 茂昭 国立がんセンター東病院内科
【 要旨 】 腺腫を含む胃ポリープ(胃隆起性病変)の前癌病変としての意義について自験例を中心に検討した.生検追跡例の成績からみると,胃過形成性ポリープの癌化は十分にありうるが,その頻度は低く前癌病変として格別に評価するには至らないと考えられた.これに対して胃腺腫では腺腫内癌が切除例中の15%を占め,経過観察例における病変増大率は18%,異型度の増加率は29%,悪性化率は5.2%と,他の良性胃病変に比してmalignant potentialは明らかに高いと評価された.加えて,生検組織学的には,よく分化した癌との鑑別が困難であり,これまで指摘されているように臨床的にはいわゆる前癌病変として取り扱うべきと思われた.しかし,胃腺腫そのものが癌化するか否かについては,生検結果が良性から悪性に転じた経過観察例をもってしても,当初から癌巣を含んだ病変であったか否かを検証することは困難であった.この点について分子マーカーを用いた検討成績をみると,筆者らのp53の過剰発現の検索からは腺腫と癌との連続性は否定的であったが,p27の発現減弱等のなどの見地からは,悪性化を引き起こす腺腫ですでに分子生物学的な異常が組み込まれている可能性も報告されている.このように腺腫の癌化についての明確な結論は今後のさらなる検索に委ねられると思われるが,いずれにせよ,少なくとも胃内に局在する病変としては腺腫のみがもっとも妥当な前癌病変として位置づけられる.
Theme Precancerous Lesions in the Digestive System
Title Gastric Premalignancy in Hyperplastic Polyp and Adenoma
Author Shigeaki Yoshida National Cancer Center Hospital East
[ Summary ] Gastric hyperplastic polyps have been shown to have a malinant potential because of the presence of those that exhibit focalized cancers historogically and malingnant changes in follow up cases examined using biopsies. In spite of this, the extremely low incidence of such casesand the rapid decrease in number of hyperplastic polyps the past decade, strongly suggests the minimal significance in relation to gastric premalignancy.
In contrast, gastric adenomas, of which more than 90% display an elevated appearance macroscopically and accompany extensive intestinal metaplasia histologically, appear to be a more specific premalignant lesions than atrophic gastritis alone. About 30% of the 890 adenoma cases endoscopically examined at the National Cancer Center were associated with cancerous changes within the adenomatous lesion or elsewhere in the stomach, suggesting a similar underlying histogenesis of the two neoplasms .In addition, according to the results of our study of 77 lesions, followed up with biopsies for more than 3 years, 14 of the lesions (18%) enlarged in size, and 9 of the 14 cases increased their histological atypism during the follow up period. In addition, 4 cases out of the 9 were diagnosed as malignant more than 5 years after the initial biopsy. These findings may confirm the close relationship between gastric adenoma and carcinoma, but the accuracy of histological diagnosis using extremely small biopsy specimens and the heterogeneity of cellular and/or structural atypism in cancerous lesions may cause problemswith diagnosis, particularly in cases with a "very well differentiatedtubular adenocarcinoma". Endoscopic mucosal resection(EMR) is certainly a worthy procedure to produce an accurate histological diagnosis,particularly for those displaying high risk endoscopic findings. Because thosewith well differentiated adenocarcinoma similar to adenoma histologically have extremely low incidence of submucosal invasion andmetastasis, regardless of their size, they can be cured with full resection using EMR.
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