術前の内視鏡治療適応の判断と根治性の評価が困難であった組織混在型早期胃癌の1例

Mixed-type Early Gastric Carcinoma with Difficulty in Judging the Possibility of Preoperative Endoscopic Treatment and Evaluating Curability, Report of a Case

要旨●患者は60歳代，男性．白色光通常内視鏡観察で，胃体下部から前庭部の広い範囲にわたり，主に褪色調，一部に発赤が混在した粘膜領域を認めた．病変の境界が一部不明瞭であったが，詳細なNBI併用拡大観察で，病変の全周にわたり範囲診断が可能であった．生検で中分化管状腺癌と診断されたが，白色光通常内視鏡観察では平坦な褪色粘膜領域を認め，NBI併用拡大観察ではVEC patternが確認されたことから組織混在型早期胃癌を疑った．しかし，未分化型癌の範囲を同定することは困難であった．同病変に対してESDを施行し，一括切除を行った．切除検体の病理組織学的所見は，組織混在型粘膜内癌で，脈管侵襲はみられず，切除断端は陰性であった．本症例は腫瘍組織内に分化型癌と未分化型癌が入り乱れて混在しており，未分化型癌のみの病変径を計測することは甚だ困難で，根治度の評価に苦慮した．早期胃癌の治療方針を決定する際，組織混在型早期胃癌に対する認識は重要であるが，内視鏡観察による腫瘍の組織型診断は現状では限界がある．

　The patient was a male in his sixties. Conventional white light endoscopy revealed a mucosal region with a largely discolored tone, combined with redness in some parts, over a wide area from the lower body to the vestibule. The lesion's boundary was partially unclear, but detailed and magnified observation combined with NBI enabled a diagnosis covering the entire lesion's circumference. The patient was diagnosed with a moderately differentiated tubular adenocarcinoma as a result of the biopsy, but conventional white light endoscopy revealed a flat discolored mucosal region, and magnified observation combined with NBI confirmed a VEC pattern. Hence, early gastric carcinoma with mixed-type histology was suspected. However, it was difficult to identify the area of undifferentiated carcinoma. ESD was performed on the same lesion, followed by en bloc resection. Histopathological findings of the resected specimen revealed intramucosal carcinoma with mixed-type histology. Furthermore, there was no vascular invasion, and the resection stump was negative. In this case, a mixture of differentiated and undifferentiated carcinoma was present in the tumor tissues, and it was particularly difficult to measure only the diameter of the lesion's undifferentiated carcinoma, which made it challenging to elucidate curability. When deciding the treatment strategy for early gastric carcinoma, it is important to have knowledge on early gastric carcinoma with mixed-type histology ; however, currently there are limits to observation-based histological diagnosis of tumors using endoscopy.