早期大腸癌の病理学的検討

A Pathological Study of Early Colorectal Carcinoma

要旨　早期大腸癌の発育形態は粘膜内隆起性発育を示すもの（PG＋）と，粘膜下浸潤による隆起性病変（PG－）とに分けられた．PG（＋）は早期癌132病変中114病変（86.4％）で，その大きさは平均17.9mmであった．このうち59病変は有茎性で，2例を除いて腺腫由来の癌であった．これらの粘膜下浸潤は極めて頻度が低く（10.2％），かつそのほとんどは微小浸潤であった．広基性を示すPG（＋）癌は平均20.5mmで，これも高頻度に腺腫由来の癌であった（89.1％）．粘膜内隆起性発育を示さないPG（－）早期癌は18/132病変（13.6％）あったが，その大きさは平均10.7mmとPG（＋）癌に比較して小さかった．これらはすべて粘膜下層に結節性浸潤を示し，かつリンパ管および静脈内浸潤が高度にみられた（72.9％）．PG（－）癌は腺腫併存が全くみられず，PG（＋）癌と異なり10mm以下の小さいde novo病変より粘膜下に浸潤した癌と考えられた．

　The growth mode of early colorectal cancer was classified into two types (Fig. 1). The first type is intramucosal polypoid growth and the second non-polypoid intramucosal growth which shows mainly submucosal massive infiltration of carcinoma, Polypoid growth type was observed in 114 out of 132 (86.4%) lesions with a mean size being 17.9 mm in diameter. In this group, 59 showed pedunculated lesions suggesting an adenoma-cancer sequence except for two cases. These cases had a low incidence (10.2%) of submucosal infiltration, and furthermore, most of the cases had a minute or scattered invasion into the submucosa. Another polypoid lesion (mean size 20.5 mm) had a broad base and a high frequency of adenoma-cancer sequence (89.1%). Submucosal invasion in these lesions was mild. Intramucosal non-polypoid early colorectal carcinomas were seen in 18 lesions out of 132 (13.6%). This type of early carcinoma was smaller (10.7 mm in diameter) than the polypoid type. All such cases were shown to have massive invasion with a high frequency of intralymphatic and venous invasions (72.2%) in the submucosal layer. Non-polypoid type was not associated with adenoma.

　This type of cancer probably developed from de novo carcinoma of less than 10 mm in size. It is of special interest that almost all cases of advanced colorectal carcinomas were of the non-polypoid type.