Ⅱa＋Ⅱc型早期胃癌の病理

Pathology of Ⅱa+Ⅱc Type Early Gastric Cancer

　Ⅱa＋Ⅱc早期胃癌は中央に浅い陥凹性変化を示すほぼ輪状の隆起性病変で，その特徴ある形状から興味が抱かれている．また井口らは早期胃癌の術後予後を追究して，この型の症例中にしばしば肝転移による早期死亡例のみられることを指摘し，そのPen型発育の定型例として掲げて以来，予後との関連の点からも注意を集めている．

　診断技術の向上に伴って隆起性病変の症例の比率が次第に増しつつあり，Ⅱa＋Ⅱc型胃癌の経験も同時に数を増しつつあるが，その頻度は，林田の集計による早期胃癌2,364例中154例，佐野の報告によれば300例中22例が経験されており，筆者の手もとの早期胃癌160例中8例を数え，この型の症例は全早期胃癌の5～7％であることが知られる．

　The so-called Ⅱa+Ⅱc early cancer of the stomach is more interested because of its characteristic appearance and early invasive growth. Its frequency among all types of early gastric cancer is estimated as 5.5 to 7.0 per cent, although its interpretation is somewhat different according to the criteria of examining institutions. The lesion of Ⅱa+Ⅱc type mostly develops on the antral mucosa in persons in the 6th and 7 th decades of age.

　Pathologically, its typical gross appearance is divided into two groups. The one is a flat polypoid growth with box-like elevation of the muscularis. The malignant cells spread to the surrounding elevated area and submucosal invasion is not so frequent. The others likely show the box-like elevation of the muscularis rnucosae, but malignant change is limited within the central Ⅱc area. The surrounding benign mucosa forms a core at an acute angle on both sides. Histologically, papillary adenocarcinoma with clearcytoplasmic cells is in most but solid medullary carcinoma are also observed. Both tend to invade the submucosa in earlier stage of cancer development. The former is more apt to show vascular invasion. Further observations not only on this type of early cancers but also on advanced carcinomas of the same variety revealed that the structure of solid medullary carcinoma in these cases was partly intermixed with papillary adenocarcinoma with clear-cytoplasmic cells. Vascular invasion was remarkable together on both caces so that histologically they appear to be of fairly approximate nature. Since clear cells are scattered about in many tubuli as Paget's cells in the mucosa of some Ⅱa+Ⅱc lesions with submucosal papillary growth of clear cells alone, these mucosal cells are of interest as representing yet an earlier stage of this type of early cancer.

　Reference has also been made to an assumption that Borrmann type Ⅱ advanced cancer with marked vascular invasion may possibly develop from this variety. Reported are also some cases of verrucous gastritis simulating Ⅱa+Ⅱc lesion.