早期胃癌臨床診断の実態―FGSによる診断水準の年代的推移

Chronological Changes in the Standard of Diagnosis by FGS for Early Gastric Cancer

　早期胃癌の肉眼的形態分類が，日本内視鏡学会によって制定された1962年は，内視鏡の分野では，1958年米国のHirschowitzが創始したファイバースコープが初めてわが国に輸入され，さまざまな欠点を有しながら，従来の胃鏡に優る動的観察性能が注目を浴びた年でもあった．

　この1962年以前の時代には，粘膜癌や初期潰瘍癌の病理組織学に関する先駆的な研究があったが，臨床的に早期胃癌がX線や内視鏡でどうにか把えられるようになったのは，1950年代の末期から1960年代に入ってからのことである．しかし，1962年早期胃癌の肉眼的分類が試案として提案された段階では，未だ今日のような早期胃癌の診断規準は確立していなかった．その後，この内視鏡学会分類を規準として，諸家により多数の症例が集積され，その切除胃肉眼所見や病理組織所見と，X線および内視鏡像を対比することにより次第に早期胃癌の診断規準が確立され，さらに今日のような微細病変の診断も可能になるまで発達したということができる．

　Changes in the diagnostic levels of FGS endoscopy for early gastric cancer have been investigated on the results obtained in our Hospital during the period June 1962 to December 1970. Of 109 cases (111 lesions) of early cancer studied by FGS prior to surgical operation, the diagnosis was correct in 87 lesions (78.4％). Of 11 cases (9.9％) interpreted at first as advanced cancer, 10 proved to be either Ⅱc or Ⅱc＋Ⅲ depressed type with sm degree of depth invasion. Endoscopy revealed in all of them thick white coat and marginal protrusions. In addition, the deformation was so apparent that we diagnosed them all as advanced cancer, but histologically only marked fibrosis was seen in the submucosa and the muscularis propriae. Of 4 cases interpreted as early cancer suspect, 3 were type Ⅱa, difficult to distinguish from Ⅱa subtype. The remaining one was Ⅱa＋Ⅱc, a well differentiated adenocarcinoma. This was likewise hard to tell from chronic erosions. In one lesion early cancer could not be ruled out, and 8 cases (7.2％) were interpreted as benign. In fact, of those initially regarded as benign, 1 case of type Ⅰ, 3 of type Ⅲ, 1 of Ⅱb＋Ⅲ and 1 of Ⅲ＋Ⅱc, where a narrow strip of Ⅱc on one side of the ulcer margin has later been confirmed, were all hard to confirm as malignancy. However, in the remaining 2, Ⅱc and Ⅱc＋Ⅲ, Ⅱc findings were overlooked. This could have been avoided.

　Chronologically considered, early gastric cancer cases have been more accurately diagnosed since the introduction of biopsy, and cases endoscopically uncertain are now definitely confirmed. Surgical correction is only exceptionally performed on cancer-suspect patients unless more exact diagnosis is arrived at. Since 1966 erroneous diagnosis of benign lesions for early gastric cancer has greatly diminuished. Establishment of biopsy in the routine examination of the stomach accounts for this good result.

　When shown in figures, the rate of accurate diagnosis for early gastric cancer differs a great deal on where to set its diagnostic criteria. False positive cases increase as false negative ones diminuish. They are in a place relative to each other.