組織混在パターン別粘膜内胃癌の臨床病理学的特徴―早期胃癌外科切除例からの検討および多施設調査結果

Treatment for Intramucosal Gastric Cancer with Mixed Type Histology（Differentiated and Undifferentiated）

要旨　外科切除された胃粘膜内癌604例を分化型腺癌と未分化型腺癌の組織混在パターンにより4つに分類し，その病理組織学的特徴について検討した．純分化型に比べて分化型優位混在型，純未分化型に比べて未分化型優位混在型は，それぞれリンパ節転移頻度が有意に高率であった．また，現行のガイドラインから非治癒切除として取り扱うこととなった“30mm以下のUL（＋）の分化型pT1a（M）で未分化型成分を有するもの”に関しては，多施設調査にて後向き研究であるが，リンパ節転移リスクが限りなく低く（0/370），治癒切除として経過観察してもよい可能性が示唆された．

　Clinicopathological data were reviewed from 604 patients who underwent surgical resection for intramucosal EGC（early gastric cancer）. Lesions were classified into four types according to the proportion of differentiated and undifferentiated components in histopathology : PD（pure differentiated）type, MD（mixed predominantly differentiated）type, MU（mixed predominantly undifferentiated）type, and PU（pure undifferentiated）type. LN metastasis was more common in MD than in PD, and in MU than in PU.

　According to the multicenter retrospective analysis, intramucosal lesions less than 30mm with ulceration without lymphovascular invasion, the rate of LN metastasis was 0％ for MD（0/370）. Further investigation is required to determine whether mixed type intramucosal gastric cancer with predominantly differentiated component, less than 30mm, with ulceration, and without lymphovascular invasion could be managed as curative resection after ESD.