完全摘除生検可能な大腸T1（SM）深部浸潤癌の術前診断―超音波内視鏡

Efficacy of Endoscopic Ultrasound to Determine the Indication of Incisional Biopsy of Colon T1 Cancer

要旨　完全摘除生検可能な大腸SM深部浸潤癌の術前診断における超音波内視鏡検査の有用性について解説した．超音波内視鏡検査は大腸癌の浸潤を垂直断面として直接観察できる唯一の検査法であり，組織上のSM浸潤距離をよく反映した．しかし，3,000μm以上のSM浸潤になると，浸潤距離の診断能が下がる傾向にあった．また，SM癌の深達度診断能は高いものの，MP癌については満足いくものではなく，その主な原因は超音波の深部減衰と考えられた．今後，低周波数の超音波内視鏡検査の併用も考慮し，より深部に浸潤したSM癌の浸潤距離診断能を向上させることが必要である．

　The present review summarized the usefulness of EUS（endoscopic sonography）for the determination of the depth of colon cancer invasion. T1 cancers with submucosal invasion of 1,000μm or more are thought to be indicative for incisional biopsy while cancers with submucosal invasion of less than 1,000μm are indicative for endoscopic resection. Establishing a method to diagnose the degree of invasion depth in cancers with submucosal invasion of 1,000μm or more is regarded to be important for determining the indication of incisional biopsy.EUS is the only imaging technique that can detect cancer invasion in a vertical dimension. In addition, it can predict the depth of submucosal invasion. However, the diagnostic accuracy of EUS decreases with submucosal invasion of ≧3,000μm. Furthermore, the diagnostic accuracy of EUS for the depth of cancer invasion with extension to the muscle layer is currently insufficient. These deficiencies were considered to be related to the attenuation of the ultrasound. Improvement of the diagnostic accuracy of EUS for the determination of the depth of cancer invasion affecting deeper layers is required to determine the indications of incisional biopsy.