隆起型の肉眼型を呈した非充実型低分化型胃癌の1例

Elevated Type of Gastric Cancer Formed by Non-solid Poorly Differentiated Adenocarcinoma, Report of a Case

要旨　患者は67歳，女性．市の胃がん検診にて異常を指摘され，前医を受診．上部消化管内視鏡検査にて胃体中部に1型胃癌を指摘され，精査・加療目的にて当科へ紹介され受診となった．胃X線検査では，胃体中部大彎に35mm大の急峻な立ち上がりを示す1型病変とその周囲に浅い陥凹性病変の拡がりが認められた．上部消化管内視鏡検査においても，胃体中部大彎に粘液の付着を伴う40mm大で発赤調の隆起性病変と周囲に拡がる浅い褪色調の陥凹性病変が認められ，病変全体は軽度の隆起上に存在していた．NBI拡大観察では，隆起部分には口径不同を伴わないネットワーク状の太い血管が観察され，周囲の陥凹部には口径不同を伴う螺旋状の細い血管が観察された．生検組織において，隆起部分では低分化腺癌が，周囲の陥凹部では中分化管状腺癌が認められた．深達度はMPと診断し，幽門側胃切除術，およびD2リンパ節郭清を施行した．切除標本において，隆起病変部は粘膜下層での著明な線維化を伴う非充実型低分化腺癌細胞の増殖により形成されており，病変の表面は肉芽組織で覆われていた．また，隆起病変部辺縁から周囲の陥凹性病変部の粘膜固有層内には中分化管状腺癌を認めた．深達度はSEであった．本症例のように非充実型低分化腺癌が潰瘍形成を伴わない隆起型進行癌を呈する例は非常にまれであり，その病理組織学的所見について文献的考察を含めて報告する．

　A 67-year-old woman diagnosed with type 1 gastric cancer at a nearby hospital presented to the National Cancer Center Hospital East. Gastric radiography showed a type 1 tumor in the great curvature of the middle body of the stomach. A lesion of 35mm in diameter with a steep, raised edge was surrounded by a shallow depressed area. Upper endoscopy confirmed a reddish, elevated lesion of 40mm in diameter that was partially covered with whitish mucus and surrounded by a discolored and shallow, depressed area in the great curvature of the middle body of the stomach. The entire lesion was elevated, presumably because of submucosal invasion. Magnifying endoscopy with narrow band imaging revealed thick, network-like vessels without caliber irregularity in the elevated lesion, and thin, corkscrew-like vessels accompanying the lesion with caliber irregularity in the surrounding depressed area. Poorly and moderately differentiated adenocarcinomas were detected at biopsy in the elevated and depressed areas, respectively. Since the tumor was thought to have invaded the muscularis propria, distal gastrostomy and D2 lymph node dissection were performed. Pathological examination of the resected specimen revealed that most of the elevated lesion was composed of poorly differentiated adenocarcinoma（non-solid type）, and that moderately differentiated adenocarcinoma existed partly in the mucosal layer. The elevated lesion was formed by the submucosal proliferation of poorly differentiated adenocarcinoma cells with marked interstitial fibrosis. The surface of the elevated lesion was covered with granulation tissues containing many blood vessels. Non-solid type of poorly differentiated adenocarcinoma rarely forms elevated gastric cancer lesions without ulcer formation. Therefore, we describe the radiographic, endoscopic and pathological findings of this case with reference to the literature regarding this type of gastric cancer.