未分化型混在早期胃癌の臨床的特徴と問題点―拡大内視鏡を中心に

Clinicopathological Feature of the Superficial Well Differentiated Gastric Adenocarcinoma with Poorly Differentiated Component

要旨　対象と方法：2006年1月から12月に佐久総合病院胃腸科にてESDが施行された分化型優位胃癌116例119病変を対象とし，占居部位，肉眼型，大きさ，NBI拡大内視鏡所見をretrospectiveに検討した．NBI拡大観察下にマーキングを施行し，全例を一括切除した．割入り後の実態顕微鏡写真上に組織型を分化型と未分化型に分類してマッピングした．マッピング写真と術前のNBI拡大写真を対比し，未分化型部分のNBI拡大内視鏡所見を検討した．結果：未分化型癌混在率は腫瘍長径20mm以下1.4％（1/73），21mm以上24.0％（11/46），隆起型6.3％（4/63），陥凹型14.3％（8/56），U領域19.4％（6/31），M領域6.5％（2/31），L領域7.0％（4/57）であり，独立した危険因子は腫瘍長径21mmであった．未分化型混在癌12症例中5例（42％）にNBI拡大内視鏡にて非network型の異常血管を認めた．他の7例中2例はsm浸潤部のみが未分化型で，粘膜内はすべて分化型癌であった．残りの5例は粘膜内の未分化型癌部分が2mm以下でありretrospectiveには非network型の異常血管を同定しえなかった．一方，2mm以下の未分化型癌を合併した7例中2例では非network型の異常血管が認められており，prospectiveに検討すれば正診率が向上することが期待された．結論：未分化型混在癌の危険因子は長径21mm以上の癌で，NBI拡大観察では未分化型癌部に非network型の異常血管を認めた．

　Patients and methods: One hundred and sixteen patients who had a differentiated dominant gastric adenocarcinoma and were treated by ESD from Jan. to Dec. 2006 in Saku Central Hospital were investigated in this study. All cases were observed by NBI magnified endoscopy and en bloc resection was performed. The resected specimens were cut in every 2 or 2.5mm steps and histological examination was performed. Mapping according to histological type was performed on the fixed specimens and the findings of NBI magnified endoscopy were compared with the mapping.

　Result: The ratio of undifferentiated mixed type was 1.4％ (1/73) in the 20mm or less group, 24.0％ (11/46) in the 21mm or more group, 6.3％ (4/63) in the protuberant type, 14.3％ (8/56) in the depressed type. Location in the upper part was 19.4％ (6/31), in the middle part 6.5％ (2/31), and in the lower part 7.0％ (4/57). The risk factor was 21mm or more (p＜0.001).

　Non-network irregular vessels were observed by NBI magnified endoscopy in 5 of 12 cases. Poorly differentiated adenocarcinoma was observed only in the submucosal layer in 2 cases. The area of poorly differentiated adenocarcinoma was 2mm or less in size in the other 5 cases. On the other hand, non-network irregular vessels were observed in two of seven cases which had minute poorly differentiated adenocarcinoma 2mm in size or less.

　Conclusions: The risk factor of well differentiated adenocarcinoma with a poorly differentiated adenocarcinoma compartment was 21mm or more in size. Non-network irregular vessels were observed in the poorly differentiated area by NBI magnified endoscopy.