LSTの超拡大内視鏡観察

Ultra-high Magnification Endoscopic Observation of Laterally Spreading Tumors

要旨　大腸腫瘍性病変の中でも側方発育型腫瘍（laterally spreading tumor ; LST）は，最大径10mm以上の側方浸潤を主体とした発育進展様式が特徴的な腫瘍である．その大きな腫瘍径により4亜型に分けられ，おのおのの臨床病理学的特徴を理解しつつ診断・治療に当たることが重要である．一体型超拡大内視鏡（CF-Y0001，prototype，オリンパス社製）により拡大倍率450倍の画像取得が可能になり，pit patternによる構造異型診断のみならず，核異型の所見を基に新しい診断学が展開されつつある．腫瘍・非腫瘍の診断では正診率97.1％，SM深部浸潤の診断では正診率96.0％と非常に高い診断能を得られた．とりわけ，表面平坦型腫瘍であるLSTはその他の肉眼形態と比べ比較的良好な画像が得られやすいので，今後さらに症例を検討し，将来的には大腸用超拡大内視鏡（endocytoscopy ; EC）診断により，さらに精度の高い深達度診断を展開していける可能性がある．

　Laterally spreading tumors（LSTs）are distinguishable from other types of colorectal tumorous lesions by their characteristic laterally spreading growth pattern which has a minimum diameter of 10mm. The diagnosis and treatment of LSTs depend on the clinicopathological characteristics of their 4 subtypes. Ultra-high magnification endoscopy（CF-Y0001 ; Olympus）has made it possible to obtain images that are magnified 450 times. This has led to ongoing development of a new type of diagnostic method based not only on the detection of structural atypia from pit patterns but also nuclear abnormalities. The diagnostic accuracy of this method is extremely high with a correct diagnostic rate of 97.1％ of neoplastic lesions and non-neoplastic lesions, and that of 96.0％ of submucosal invasion. In particular, it is easy to obtain satisfactory images of LSTs as they are flat lesions, in contrast to those of other morphological types. Further studies of LST cases will allow development of increasingly accurate invasion-depth diagnosis methods using endoscopic classification（EC）.