びまん浸潤型大腸癌の診断

Diagnosis of Diffusely Infiltrating Carcinoma (Linitis Plastica) of the Colon

要旨　1977年大腸癌取扱い規約で，大腸に原発するlinitis plastica癌は，びまん浸潤型大腸癌に統一され，その臨床および病理学的特徴が徐々に明らかにされつつある．筆者らはこの範疇に属する大腸癌を過去13年間に12例経験し，大腸癌全体に占める頻度は1.8％であった．平均年齢は51.5歳と若年に多い傾向にあり，男女比は2：10と圧倒的に女性に多い．発生部位は直腸，S状結腸が10例（83.5％）と下部大腸に多く，予後も不良で，早期発見も困難を極めている．本症はlong segmentにわたる腸管の狭窄，硬化，不整を特徴とし，たとえ完成された病変であっても炎症性疾患との鑑別に苦慮する症例もまれならず経験されている．本稿では自験例を中心に本症の診断上の問題点，今後の早期像の解明の重要性につき述べた．

　Diffusely infiltrating carcinoma (linitis plastica) of the colon is defined, as a pathological entity, by two morphological characteristics ; macroscopic appearance of rigid tubular thickening involving long segment of the colon and microscopic appearance of poorly differentiated adenocarcinoma composed of a pleomorphic cell population. During the last 13 years we have experienced 12 documented cases of primary diffusely infiltrating carcinoma of the colon, accouting for 1.8% of all operated cases of colonic disease. Ten cases (83.3%) were females, with a mean age of 51.5 years. The symptomatology of illness is usually related to the degree of the involvement of the colon and the average duration of symptoms prior to presentation was very short, less than three months. A change in bowel habit (diarrhea, constipation and tenesmus) was noticed in 83.3% of patients with 30% presenting with colonic obstruction. Primary lesion of this type of the carcinoma occurred most frequently in the rectosigmoid (10 of 12 cases) with the remaining 2 cases in the descendig colon.

　The prognosis was very poor due to its late presentation. The median survival was 5 months (3-9 months) when peritoneal dissemination had occurred. Hence, the most important implication is to diagnose at earlier stage of this disease. There are some cases which may present with an atypical appearance and radiographic features suggestive of an inflammatory strictures involving long segment of the colon due to Crohn's disease, diverticulosis or ischemia. So, it is sometimes difficult to make differentiation from inflammatory diseases involving long segment of the colon. With such equivocal findings, we recommend from our experiences, biopsies using thin fiberscope or brush cytology be done.