食道粘膜癌の内視鏡診断―深達度亜分類を用いた深達度診断の検討

Endoscopic Estimation of Depth of Invasion in Cases with Esophageal Mucosal Cancer

要旨 　食道粘膜癌の深達度診断は，治療法を選択する上で重要であり，現時点の目標は，局所治療で根治可能な粘膜固有層内に止まるm₁～m₂癌と外科治療が必要なm₃癌の鑑別である．食道表在癌132例を内視鏡病型から，隆起型0-Ⅰ（33），軽度隆起型0-Ⅱa（16），平坦型0-Ⅱb（15），軽度陥凹型0-Ⅱc（56），陥凹型0-Ⅲ（12）に分類した．0-Ⅰ型の97.0％（32/33）はsm₂以上，0-Ⅲ型の66.7％（8/12）はsm₃であるのに対し，0-Ⅱ型の83.9％（73/87）はmで，Ⅱcの23.2％（13/56）にsm癌が含まれていた．Ⅱbの深達度はすべてm₁であった．Ⅱaの93.8％（15/16）はm₁～m₃で，深達度診断は隆起の高さと表面性状で行えた．Ⅱcの深達度はm₁～smまであり，陥凹の深さや陥凹底および陥凹周囲の性状による深達度診断の正診率は，Ⅱc（m₁）86.4％，Ⅱc（m₂）71.4％，Ⅱc（m₃）71.4％，治療法選択の観点からm₁～m₂とm₃の鑑別正診率は93％であった．食道表在癌の深達度診断は，色素内視鏡を併用しても90％に満たない．これは，食道壁の構造を破壊せずに浸潤したり，食道の正常構造を伝わって浸潤する病変を浅く診断し，固有筋層に対し圧排性に発育したり，癌の浸潤に高度の線維化を伴う病変を深く診断するためである．

　Incidence of lymph node metastasis, which is one of the most reliable prognostic factors in cases with super ficial esophageal cancer, shows close relationship with depth of cancer invasion. Treatment of mucosal cancer of the esophagus should be decided considering the depth of cancer invasion. At present, differentiation of intraepithelial cancer (m₁) and mucosal cancer confined to the lamina propria mucosae (m₂) from those reaching to the muscularis mucosae (m₃) is point of clinical diagnosis. Mucosal cancer with m₁ and m₂ cases rarely had lymph node metastasis and could be treated by endoscopic mucosal resection technique, but cases with m₃, 11% of all cases had lymph node metastasis and so, esophagectomy with lymph node dissection should be indicated.

　Gross classification also suggested the depth of cancer invasion. 97% of cases with 0-Ⅰ (superficial and elevated) type of lesions and 100% of 0-Ⅲ (superficial and distinctly depressed) type were submucosal cancer. On the other hand, in cases with 0-Ⅱ (superficial and flat type; 0-Ⅱa, 0-Ⅱb, 0-Ⅱc) type of lesions, 84% of them were mucosal cancer. ln cases with 0-Ⅱa type of lesions, depth of invasion was m₁, m₂ or m₃. All cases with 0-Ⅱb type of lesions were m₁ cancer. In cases with 0-Ⅱc type of lesions, 77% of all cases were mucosal cancer, while 23% was submucosal cancer. Precise estimation of depth of cancer invasion was indispensable in cases with 0-Ⅱc type of lesions. Endoscopic estimation of depth of invasion was discussed. 0-Ⅱc and m₁ lesions were estimated with accuracy rate of 86%, 0-Ⅱc and m₂ 71%, and 0-Ⅱc and m₃ 71%. Accuracy rate of differentiation of m₁ and m₂ from m₃ lesions was approximately 93%. Pathological features of cases with underestimation were cancer infiltration without destruction of anatomical structures of esophageal wall and cancer extension following ducts of esophageal glands. Depth of invasion tends to be overestimated in cases with cancer mass compressing the muscularis mucosae or the proper muscle layer. Cases with distinct fibrosis in the lamina propria mucosae or the submucosa were also overestimated in depth of invasion.