胃悪性リンパ腫のX線所見の検討―癌・RLHとの鑑別

Macroscopic and Radiologic Findings of Malignant Lymphoma of the Stomach

　胃悪性リンパ腫は，胃原発悪性腫瘍の中では比較的まれな疾患である．胃癌に対する頻度についてみると，中村ら¹⁵⁾によれば0.5～7.6％である．近年，X線・内視鏡診断技術の進歩と共に悪性リンパ腫の手術もわずかながら増加しつつある．

　悪性リンパ腫に対する初回時X線診断についてみると，病変の進行程度にかかわらず，その多くは胃癌と診断されている¹⁰⁾．癌と診断されやすい傾向にあることについて考えると，単に悪性リンパ腫と癌との鑑別が難しいことだけでなく，胃の悪性腫瘍のほとんどが癌であり悪性リンパ腫は少なく，しかも癌と悪性リンパ腫とではX線・内視鏡的によく類似した所見を示すといったことから，胃の悪性病変はすなわち癌といった観念的な診断を行いやすい状況下にあることがその原因の1つであろう．ところで，臨床診断体系の中で，良・悪性の判定に当たって最も重視されている生検組織診断成績についてみると，悪性リンパ腫病変に対する質的診断率は50～60％⁸⁾¹⁰⁾にすぎない．したがって，胃癌の場合とは異なり，胃悪性リンパ腫では最終的な良・悪性の判定をX線・内視鏡診断に頼らざるを得ないといった事態も生じてくる．このような胃悪性リンパ腫に関する臨床診断上の問題点を解決するためには，数多くの症例を集め，それらのX線・内視鏡所見を系統的に検討することが必要である．

　Radiologic diagnosis of malignant lymphoma of the stomach was studied in relation to its differential diagnosis from other gastric malignancies, especially from cancer, based on 84 foci out of 59 cases which had been operated upon in a period of 35 years from 1946 to 1980 at the Cancer Institute Hospital, Tokyo.

　Advanced malignant lymphoma is differentiated from advanced cancer in the following points; 1) Distensibility of the gastric wall was kept relatively will. 2) Filling defect was sharply defined and occured abruptly from the normal appearing wall of the lesser and greater curvature without intervening stiffening between normal gastric wall and the filling defect. 3) A wedge-shaped niche was often visualized in the filling defect. 4) Ulceration was notuniform in depth, partly being deep. 5) The surrounding raised wall was usually smooth and sharply circumscribed. 6) There was a sign of submucosal tumor in some part of a lesion. 7) In giant rugal type the edematous, thickened folds were rather straightened. The lesion often accompanies multiple ulcers or tumor formations.

　Early malignant lymphoma could be differentiated from early cancer in the following points; 1) In Ⅱa＋Ⅱc type flat mucosal elevation with central depression was characteristic. 2) Ⅱc type could be distinguished from early cancer, Ⅱc, of undifferentiated type with difficulty. Sometimes, however, limit of depression could not be defined clearly on the radiologic findings despite that it was clearly defined on the resected specimen. Surface granularity in the depression was smooth and densely distributed. If a Ⅱc type partly accompanied slightly raised wall, its margin was smoothly outlined. 3) The differential diagnosis from RLH was difficult in most cases. Some change in the radiologic findings obtained in the follow-up study could often be of help for the differential diagnosis.