LSTの定義・細分類とその臨床的意義

Definition and Subclassification of LST in Relation to Clinical Significance

要旨　大腸LST（laterally spreading tumor）とは，“最大径10mm以上の水平発育する大腸腫瘍群に対する呼称”であり，世界中で広く使用されている．「大腸癌取扱い規約」にはこれまでLSTという用語は掲載されていなかったが，2013年7月発刊の「大腸癌取扱い規約第8版」にその定義や画像が掲載された．なお，LSTは，肉眼型を示す用語ではなく，食道や胃で使用されている“表層拡大型腫瘍”というニックネームと同義である．本稿では，典型例の内視鏡画像を示しながら，LSTの定義・細分類とその歴史的変遷と臨床的特徴について解説した．

　The term LST（lateral spreading tumor）was originally proposed by Kudo to describe colorectal tumors laterally spreading to more than 10mm in diameter. The term LST is now commonly used worldwide. However, the term LST had not been described in the General Rules for Clinical and Pathological Studies on Cancer of the Colon, Rectum and Anus（edited by the Japanese Society for Cancer of the Colon and Rectum）. The definition and concrete colonoscopic images of LST have now been included in the 8th edition of the revised version, published in July 2013. The term LST is not used for macroscopic carcinoma but is a subclassification similar to superficial spreading tumor for esophageal and gastric carcinoma. In this report, we explain the history and clinical significance of LST subclassification, including the relationship with each clinicopathological feature.