ESDからみた未分化型混在早期胃癌の取り扱い―断端再発，リンパ節転移を含めて

ESD Treatment for Histologically Mixed-type Early Gastric Cancer (Including Recurrence and Metastasis to the Lymph Node)

要旨　ESD前の生検で分化型であり治療を行った早期胃癌440例中，未分化混合型であった29例について検討を行った．術後病理診断で，分化型であったもの（分化純型）は411例（93.4％），10％以上に未分化型の混在のあったものは29例（6.6％）であった．分化純型ではSM癌が17例（4％）に対し29例の未分化混合型ではSM癌は14例（48％）あり，有意に高率であった．SM浸潤度別では分化純型でSM2が8例（47％）に対し，未分化混合型で10例（71％）と高率であった．またSM癌における脈管侵襲率は，分化純型SM1で1/9（11％），SM2で5/8（63％），未分化混合型SM1で3/4（75％），SM2で6/10（60％）に認め，未分化混合型SM1癌の脈管侵襲率が高率であった．未分化混合型SM癌については12例が追加胃切除術，2例が経過観察されている．胃切除術例についてリンパ節転移はみられなかった．未分化混合型の不完全切除例と遺残再発例は3例あり，遺残病変からの再発が確認された．これら3例は全例範囲診断が困難であり，特徴は手つなぎ腺管を有するtub2が主体であった．未分化混合型では通常の分化純型に比べSM浸潤率，脈管侵襲率が高く，範囲診断が困難であることが示唆された．

　We studied 29 cases of histologically mixed-type out of 440 cases of early gastric cancer resected by endoscopic submucosal dissection (ESD). All the cases were diagnosed by biopsy as differentiated adenocarcinoma. In 411 cases (93.4％), biopsy diagnosis and the ESD final pathological diagnosis were the same viz. differentiated adenocarcinoma. However, in 29 cases (6.6％), the biopsy diagnosis differed from the ESD final pathological diagnosis. Biopsy diagnosis indicated adenocarcinoma but the ESD final pathological diagnosis indicated differentiated or poorly-differentiated mixed-type cancers. There were 17 cases (4％) of submucosal invasive cancer that were diagnosed by both biopsy and ESD as being the same histologically. However, there were 14 cases (48％) of SM cancers which were diagnosed histologically as mixed-type.

　From the degree of submucosal invasion, there were 8 cases (47％) of SM2 cancers of differentiated type, but, in contrast to this, there were 10 cases (71％) of SM2 cancers which were histologically mixed-type. In the SM1 cancers, lymphatic and venous permeation was found in 1/9 (11％). In SM2 cancers, 5/8 (63％) cases were differentiated type, and lymphatic and venous permeation was found in 3/4 (75％) of cases of SM1 cancers, and it was found in 6/10 (60％) of cases of SM2 mixed-type cancers. SM invasion and lymphatic permeation were of higher frequency in mixed-type cancers, and lymphatic and venous permeation was especially high in frequency in SM1 mixed-type cancers. 12 cases of SM mixed type cancers were surgically operated on after ESD. There was no lymph node metastasis in operated cases. 2/394 (0.5％) cases were found to be incompletely resected cases in the differentiated type cancers, but 3/15 (20％) were found to be incompletely resected cases in the histologically mixed-type cancers. Also, in 3 cases of incomplete resection residual lesion was detected in the histologically mixed-type cancers. In all cases it was difficult to correctly diagnose the boundary of the lesion. And all the cases had a histological appearance like moderately differentiated adenocarcinoma. We showed in this study that histologically mixed-type well-to-poorly differentiated adenocarcinoma was likely to invade the submucosa and had a high frequency of lymphatic and venous peameation, and it was difficult to make a correct diagnosis of the boundary of the lesion.