Differences Between Early PG-type and NPG-type Colorectal Carcinomas:Including Growth and Progression Patterns Masahiro Ikegami 1 , Shinichi Hirooka 1 , Mayo Nakamura 1 , Daisuke Aizawa 1 , Nei Fukasawa 1 , Keishiro Murakami 1 , Rei Makishima 1 , Hiroko Kimura 1 , Noriko Hosaka 1 1Department of Pathology, the Jikei University School of Medicine, Tokyo Keyword: 早期大腸癌 , PG/NPG分類 , 発育・進展 pp.810-818
Published Date 2019/5/25
DOI https://doi.org/10.11477/mf.1403201755
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 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.

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