内視鏡診断からみた大腸pm癌の特徴

Characteristics of Endoscopic Features of Proper Muscle (pm) Colorectal Cancer

要旨　大腸pm癌の内視鏡所見の特徴を内視鏡観察されたpm癌56例（男性：24例，女性：32例）を対象として検討した．pm癌の全大腸癌に占める頻度は5.2％であった．部位別頻度では直腸57.1％であり，sm癌（32.8％），ss（a₁）癌（35.6％）に比し直腸に多い．pm癌は長径34.4±12.2mmでsm癌18.3±9.2mm，ss（a₁）癌51.3±15.1mmと有意の差（ρ＜0.01）を認めた．pm癌の肉眼型は隆起型，平皿型，平皿陥凹型，隆起潰瘍型，潰瘍型，分類不能型の6型に分類され，平皿陥凹型が43％と最も多い．pm癌は陥凹・潰瘍を伴うものが86％と多く，sm癌の14％と差がある．腫瘍に対する陥凹・潰瘍の面積比はpm癌21.5％，ss（a₁）癌39.7％と有意の差（ρ＜0.01）を認めた．

　We encountered 56 cases (male: 24 cases, female: 32 cases) of pm colorectal cancers detected in surgically resected specimens and by endoscopic observation during the last 12 years. Endoscopic characteristics of these cancers were as follows: 1) The frequency of pm cancer was 5.2% in a total of 1,084 colorectal cancers.

2) The distribution rate of pm cancer in the rectum and sigmoid colon (85.7%) was higher than that of early (76.2%) or other advanced (65.9%) colorectal carcinomas.

3) The average (±SD) maximal diameter of pm cancer was 34.4±12.2mm, which was significantly higher than that of sm cancer (18.3±9.2mm) and less than ss (a₁) cancer (51.3±15.1mm).

4) The pm cancers studied were macroscopically classified into six groups as follows; protruded type (9 cases), plate type (5 cases), plate with depression type (18 cases), plate with ulcer type (8 cases), ulcer type (2 cases) and unclassified type (2 cases).

5) Tumors with depression or ulceration were observed more frequently in pm cancers (86%) than in sm cancers (14%), and the ratio of depressed or ulcerative area per tumor area was 21.5±15.6% in pm cancers, which was smaller than that found in other adwanced cancers (39.7±12.8%).

It is concluded that, endoscopically, pm cancer has characteristics somewhere between those of sm and ss (a₁) cancers. To diagnose a pm cancer by usual endoscopic examination, it is important to observe the size and area of the depression or ulceration of the tumor.