多発粘膜下腫瘍様形態を呈した胃リンパ球浸潤性髄様癌の1例

Medullary Carcinoma with Lymphoid Stroma of the Stomach Featuring as Multiple Submucosal Tumors, Report of a Case

要旨　患者は50歳，男性．検診で異常を指摘され当科を受診した．胃X線造影，内視鏡検査で胃体中部～上部前壁に粘膜下腫瘍様隆起が約10cmにわたり非連続性に多発し，隆起の一部に浅い陥凹所見と潰瘍瘢痕を伴っており上皮性の所見としてとらえられた．超音波内視鏡所見では，粘膜下層を中心に濾胞様構造をとる比較的強い低エコーの腫瘍が第4層まで及んでいた．胃全摘術を施行した結果，病理組織学的には深達度MPの低分化型腺癌でいわゆるリンパ球浸潤性髄様癌であり，脈管侵襲やリンパ節転移は認めなかった．またEBER（Epstein-Barr virus encoded RNA）-1 in situ hybridization陽性でありEBウイルス関連胃癌と考えられた．

　A 50-year-old man visited our hospital for close examination for gastric lesions. Barium meal and endoscopic examinations revealed some submucosal tumorous lesions on the anterior wall of the gastric body, measuring about 10 cm in size. A shallow depression and an ulcer scar were demonstrated near the anal side tumor. Endosonographic examination disclosed strong hypoechoic masses in the third to fourth layer of the gastric wall composed mainly of round clustered lesions. Biopsy specimens proved poorly differentiated adenocarcinoma. Surgically resected specimens showed some submucosal tumorous elevations, one of which had a depression with an ulcer scar. Histopathologically, poorly differentiated adenocarcinoma extended into the muscularis propria with marked infiltration lymphocytes. This is the so called ‘medullary carcinoma with lymphoid stroma’. Immunohistochemical analysis indicated that Epstein-Barr virus encoded RNA-1 was positive in the nuclei of the carcinoma cells, this proving this case was an EBV associated gastric cancer.