いわゆる側方発育型大腸腫瘍の定義の歴史

Laterally Spreading Tumor of Colon―Definition and History

要旨

　大腸上皮性腫瘍の中には，ポリープのように上方向発育するものと，IIcのように下方向発育するものの他に，側方に発育進展していく腫瘍群がある．その中で腫瘍径10mmを超える同腫瘍群がLST（laterally spreading tumor）と称する．LSTは顆粒型（granular type）と非顆粒型（non-granular type）に分類されるが，前者は以前，顆粒集簇型あるいは結節集簇様病変とされていた腫瘍群に相当する．一方，それ以外にも顆粒・結節を形成せず側方発育形態をとる腫瘍群が認められるようになり，LST非顆粒型と呼称される．側方発育型の特徴を有する両者を総称しLSTとされた．近年様々な施設で，病理学的・遺伝子学的解析が行われるようになり，その臨床像が明らかになりつつあり，EMR・ESDなど内視鏡的治療が進化し続ける今日において，腫瘍の質的・量的診断は不可欠である．LSTにおいても今後さらなる解析のもとに適切な治療法が選択されることが重要である．

　Among colorectal neoplasms, there is a certain group that are likely to extend laterally, rather than vertically along the colonic wall. In the last 20 years, many cases of these tumors have been reported, and these tumors are defined as LST : laterally spreading tumor. The difinition includes only tumors more than 10mm in diameter. LST are classified into granular type and non-granular type. The tumors which have been recognized as nodule aggregating lesions are classified as granular type. The granular type are further divided into two groups ; homogeneous type and mixed nodular type. Non-granular types are divided into two more group ; flat elevated type and pseudo-depressed type. Since the term nodule aggregating lesion has been introduced, several terms which stand for these tumors have been used for expression of colorectal tumors extending laterally. Among these terms LST is the best expression for such colorectal tumors. Recently, histopathological study and mutation analysis has made the nature of LST clear. To select appropriate therapy for LST it is important to rely on such analysis.