食道表在癌の深達度診断―NBI拡大内視鏡の立場から

Diagnosis of Invasion Depth for Esophageal Superficial Cancer by NBI Magnified Endoscopy

要旨　NBI拡大内視鏡にて観察される微細血管の口径不同，血管径，延長所見に注目し，異常血管の延長所見が軽微で，血管径が細い場合に深達度T1a（EP-LPM），異常血管の延長を認めたが血管径が細い場合はT1a-MMからT1b-SM1，高度延長に加え血管径の増大を認めた場合をT1b-SM2と診断した．また有馬らが報告したAVA（avascular area）≦0.5mmをT1a-LPM，AVA＞3mmをT1b-SM2，この間をT1a-MMからT1b-SM1と診断してきた．これらの血管所見は深達度診断に有用であったが，浸潤部の表層がT1a-EP，LPMの癌で覆われた病変やT1a-MM浸潤幅が1～2mm以下であった病変では血管の異型が観察されず，NBI拡大内視鏡による診断の限界であった．通常観察にて厚みを認めたにもかかわらず，血管異型が軽度な病変に従来法であるEUSを併用した総合的な診断が望まれる．

　Recently, the usefulness of NBI magnified endoscopy for the diagnosis of invasion depth of superficial esophageal SCC has been reported. When the abnormal vessels are short and narrow, elongated but narrow, and elongated and dilated, the invasion depth was diagnosed as T1a-EP/LPM,T1a-MM/ T1b-SM1 and T1b-SM2, respectively. And, when the size of a-vascular area was 0.5mm or less,0.5mm to 3mm, and more than 3mm, the invasion depth was diagnosed as T1a-EP/ LPM,T1a-MM/ T1b-SM1, and T1b-SM2, respectively.

　When the invaded cancer was covered by T1a-EP, the diagnosis of invasion depth by NBI magnified endoscopy was difficult, because NBI magnified endoscopy can observe only the surface of the mucosa. EUS is useful for examination in such a case. When the invaded size was 1～2mm, the diagnosis of invasion depth was also difficult.

　In conclusion,NBI magnified endoscopy is useful for the diagnosis of invasion depth of esophageal superficial cancer. However, when the vascular irregularity is mild but the lesion is rather thick,EUS should be performed.