病理（マクロ像）からみた早期胃癌の深達度診断

Pathological Diagnosis of Depth of Invasion of Early Gastric Adenocarcinomas with Special Reference to Their Gross Features

要旨　早期胃癌外科切除例にみられた119病変（深達度M：60病変，SM1：12病変，SM2：47病変）を対象として，深達度と関連する肉眼所見および対応する組織学的所見について検討した．内視鏡的切除の適応となりうる大きさ2～3cmの病変は，同時にSM癌が最も多い領域であることに注意する必要がある．組織学的に確認されたSM浸潤部とSM浸潤によって生じた肉眼所見との明確な対応を確認できたものは，SM2癌の66％（31/47病変）であった．SM1癌および約半数のSM2癌はSM浸潤部全体に粘膜内癌成分を伴っており，SM浸潤部の病変表面への露出がSM浸潤を診断する主所見となる病変は限られた．一方，SM浸潤に伴う粘膜要素の挙上およびそれに関連した変化はSM浸潤の肉眼診断において認識すべき重要な所見とみなされたが，その所見がみられた病変の多くはSM浸潤距離＞2,000μmかつSM浸潤幅＞0.5cmであった．潰瘍・潰瘍瘢痕（UL）の合併は，陥凹面の不整・粗糙所見からの深達度診断を困難とするひとつの要因と考えられた．肉眼的なSM浸潤診断が困難なもうひとつの病変として，粘膜内癌成分が保たれた癌のリンパ管侵襲によるSM浸潤がある．肉眼所見からの深達度診断を困難とする要因をよく認識したうえで切除検体の十分な病理組織学的検索を行うことの重要性が再確認された．

　We analyzed 119 surgically resected early gastric cancers, which included 60 lesions limited to the mucosa（M cancers）and 59 lesions infiltrating to the submucosa（SM cancers）, to highlight gross and histologic features with regard to their submucosal invasion. It should be noted that the lesions with maximum diameter of 2-3cm, which are resectable endoscopically, frequently showed submucosal invasion. Dividing SM cancers into 12 SM1 cancers and 47 SM2 cancers based on their depth of invasion, gross alterations at the histologically confirmed submucosal invasion sites were identified in 31 out of 47（66％）of SM2 cancers. In all of the SM1 cancers and in about half of the SM2 cancers, intramucosal carcinoma was wholly preserved at the submucosally invasive areas, and this is one of the factors which make the diagnosis of depth of invasion difficult. One noted finding helpful in the diagnosis of submucosal invasion was the elevation of mucosal elements as a result of the invasive cancer mass. In the present series, such lesions showed an invasion distance of＞2,000μm and the width of the invasion area was＞0.5cm. The diagnosis of submucosal invasion could be complicated by the association of ulcer and/or ulcer scar（UL）in depressed cancers. Another challenging situation is submucosal invasion through lymphatic vessels which show few gross changes suggestive of submucosal invasion. Recognizing the factors that would make the gross diagnosis of submucosal invasion difficult, thorough examination of the resected materials is mandatory.