未分化型混在早期胃癌の臨床的特徴と問題点―通常内視鏡診断を中心に

Clinical Features and Issues of Early Gastric Cancer Which Consist with the Elements of Well and Poorly Differentiated Adenocarcinoma―Mainly by Conventional Endoscopy

要旨　リンパ節転移の可能性が低い早期胃癌に対して内視鏡的粘膜下層剥離術（endoscopic submucosal dissection；ESD）が積極的に施行されるようになったが，未分化型混在早期胃癌に対する臨床的な対応は統一されていない．2001年4月から2007年4月までに南風病院で手術された胃粘膜内癌（主病変に限る）は171病変であった．内訳は分化型癌88病変，分化型癌と未分化型癌の混在型（未分化型混在癌）22病変，未分化型癌61病変であり，この中で未分化型混在癌22病変の形態的特徴を検討した．病変の大きさは1.3～9cmで平均3.8cmであった．肉眼型はすべて陥凹主体で潰瘍（瘢痕）の合併が11病変にみられた．術前の検査で潰瘍（瘢痕）を指摘していない病変が3病変存在した．内視鏡検査で病変の色調は，発赤調主体が8病変，褪色調主体が8病変，正色調主体が6病変であり，発赤調主体の病変は約1/3にとどまった．病変（陥凹面）の性状は胃小区類似の模様が10病変，大小顆粒状模様が11病変，胃小区が不明瞭化した平滑模様が1病変であり，分化型癌と未分化型癌の中間的な形態を呈していた．内視鏡検査で病変の境界がほぼ全周性に追えるものは8病変，半周以上追えるが全周性には追えないものは11病変，半周未満しか追えないものは3病変であり，境界不明瞭な病変が多かった．未分化型成分が領域をもつ病変では陥凹面に大小顆粒状の模様がみられ，未分化型成分の存在を推測可能なものが存在していた．しかしながら，未分化型成分が領域をもたず散在性に混在する病変では陥凹面の性状のみで未分化型成分の存在を指摘するのは困難であった．切除標本の病理組織学的検討が重要であり，現時点においては未分化型混在癌と診断された場合にはリンパ節転移の危険因子と考えて慎重に対応すべきである．

　Although endoscopic submucosal dissection (ESD) has been developed and widely accepted for early gastric cancer that is expected not to metastasize to the lymph nodes, consensus has not been reached on the treatment for well differentiated early gastric cancer complicated with the element of poorly differentiated carcinomas. In Nanpuh Hospital, 171 patients with intramucosal gastric carcinoma underwent surgery between April 2001 and April 2007. Eighty-eight and 61 lesions were diagnosed as well differentiated and poorly differentiated adenocarcinoma, respectively. The other 22 lesions consisted with the elements of well and poorly differentiated adenocarcinoma and were evaluated in this study. The tumors ranged in size from 1.3 cm to 9 cm, with an average of 3.8 cm. On macroscopic findings, all cases had mainly depressed lesions and 11 cases had ulcers or ulcer scars. Of 11 cases, three lesions had not been detected on preoperative examinations. The lesions were reddish in 8 cases, discolored in 8 cases and normal in color in 6 cases. The properties of the depressed surfaces of the lesions were similar to the gastric area in 10 cases, 11 cases had a large and small granulated pattern, and one case has a flat and smooth surface resulting from the indistinct gastric area. The macroscopic appearance was intermediate between poorly and well differentiated carcinoma. On endoscopic examination, 8 lesions showed distinct margins around the entire circumference, 11 had distinct margins on more than half but less than the whole circumference, and 3 had distinct margins on less than half the circumference, and therefore had mostly indistinct margins. The lesions which had some areas of poorly differentiated adenocarcinomas showed a large and small granulated pattern in the depressed surfaces, which allowed us to determine the location of the poorly differentiated carcinoma. However, in the tumor with scattered elements of the poorly differentiated carcinoma, it was not possible to determine the location of the poorly differentiated carcinoma based on the characteristics of the depressed surfaces. The cases which consist with the elements of well and poorly differentiated adenocarcinoma on histopathological investigation of resected specimens require careful treatment due to the risk of lymph node metastasis.