m3・sm1食道癌の内視鏡超音波診断

Endoscopic Ultrasonography for Patients with an Esophageal Cancer Invading to the Deep Mucosa or Superficial Submucosal Layer

要旨　食道表在癌の内視鏡超音波診断には高周波数細径プローブが適しており，内視鏡観察に引き続き微細な超音波断層所見の評価が可能である．20MHz細径プローブを使用した場合，食道壁は9層構造をとることが多いが，従来型超音波内視鏡による5層構造に対応させて考えることができる．臨床的に良い画像を得るために工夫は必要であるものの，検査自体難しい手技ではない．粘膜筋板に由来する超音波層を判読することが臨床診断の基盤となる．これにより，粘膜癌と粘膜下層癌の鑑別をはじめ，腫瘍の壁内伸展状況など，詳細な超音波断層診断が可能で，m₃・sm₁病変の精密診断にも応用できる．しかし，微小浸潤やリンパ組織増生の診断には問題が残されている．

　An examination using a high frequency ultrasound thin probe is one of the most appropreate means for the evaluation of superficial esophageal cancers. Detailed examination of the ultrasonic structure of the esophagus following conventional endoscopic observation is possible. Using a 20 MHz ultrasound thin probe in esophageal endoscopy, it is possible to measure nine sono-layers, where as only five sono-layers are able to be recognized using traditional EUS examination. Although there are some technical points necessary to obtain good ultrasound figures, the technique of endosonography using an ultrasound thin probe is not difficult. Defining the muscularis mucosa in terms of sono-layer is the most important step in the pretreatment diagnosis for superficial esophageal tumors. Endosonography using a thin probe is useful in differentiating between mucosal and submucosal tumors, detecting the pattern of intramural spread of the tumor, and so on. However, the diagnosis of microinvasion of the tumor and the differentiation between tumor invasion and lymphoid hyperplasia still poses problems.