PG typeとNPG type早期大腸癌の相違—発育・進展様式を含めて

Differences Between Early PG-type and NPG-type Colorectal Carcinomas:Including Growth and Progression Patterns

要旨●早期大腸癌を，その割面形態からPG（polypoid growth）typeとNPG（non-polypoid growth）typeの2種類に分類し，それぞれの病変の特徴について明らかにするとともに，大腸癌の発育・進展について検討した．NPGはPGに比較して少ない病変であった．PGでは腺腫併存病変が多かった．NPGはPGと比較して小さいうちから粘膜下層（SM）に高度に浸潤する病変であった．また，粘膜（M）における増殖細胞の分布やDNA定量の結果からも，PGとNPGは生物学的に異なる病変と考えられた．大腸SM癌をPG粘膜下層浸潤癌（PG SM），NPG粘膜下層浸潤癌（NPG SM）別に分け，特にNPG SMを粘膜内病変保存例と非保存例に分類し解析したところ，大腸SM癌のうち確実に隆起型病変（PG M）に由来するものが約64%と多くを占めた．表面型病変（NPG M）から由来したと考えられるSM癌の頻度は確実な値としては18%程度と少数であり，多くとも約36%以下であると考えられた．20mm以下進行大腸癌の解析から，20mm以下進行癌を形成する病変は，NPG SM癌由来と考えられるものが89%と多く，少なくとも小さな（20mm以下）進行癌の形成にはNPG病変，言い換えると表面型M癌が深く関与していると考えられた．

　Early colorectal cancers can be classified into two types according to their cross-sectional configuration, namely, the PG（polypoid growth）type and the NPG（nonpolypoid growth）type. We have catalogued the characteristics of each type of lesion and investigated their growth and progression in the context of colorectal cancer.

　The occurrence of NPG carcinomas was relatively rare compared with PG carcinomas ; the latter, in the majority of cases, coexisted with adenomas. NPG carcinomas displayed a high degree of infiltration into the submucosa（SM）while still small compared with PG carcinomas. Based on the distribution of proliferating cells and the quantity of DNA in the mucosa（M）, it is surmised that NPG carcinomas are biologically different from PG carcinomas.

　Submucosal colorectal carcinomas were classified as either invasive PG submucosal carcinomas（PG SM）or invasive NPG submucosal carcinomas（NPG SM）. When NPG SM cases were classified according to the presence or absence of unresected lesions in the submucosa, analysis showed that approximately 64% of submucosal colorectal carcinomas originated from protruding lesions（PG M）. If a definite figure must be given for the frequency of submucosal carcinomas that originate from surface lesions（NPG M）, then this can conceivably be quite low, at just 18% ; it is surmised that at most the figure would not exceed 36%.

　Analysis of colorectal carcinomas that were ≦20mm in diameter showed that among lesions that formed advanced carcinomas ≦20mm in diameter, 89% originated from NPG SM carcinomas. To summarize, NPG lesions（i.e., mucosal carcinomas）can be heavily implicated in the formation of small（≦20mm in diameter）advanced carcinomas.