OBJECTIVETo observe and summarize the morphologic features that may suggest submucosal invasive adenocarcinoma in colorectal mucosa biopsy specimens.

METHODSThe study cohort included 432 colorectal biopsy specimens were obtained from 2006 to 2012. All the cases had radical surgery. Basing on the pathologic diagnoses, the cases were divided into 366 invasive adenocarcinoma (IAC) and 66 high-grade intraepithelial neoplasms (HGIN). These two groups were compared.

RESULTSIn the IAC group, the percentage of tumor forming cribriform structures, acute angle-shaped glands, diffuse carcinoma cell proliferation was 61.2% (224/366) , 33.8% (124/366) and 7.4% (27/366) , respectively. In the HGIN group, cribriform gland structures appeared in 6.0% (4/66) of the cases, while no acute angle-shaped gland or diffuse carcinoma cell proliferation was detected. The difference of these three characteristics in the two group was statistically significant (all P < 0.01). Glandular branching was detected in 89.9% (329/366) of IAC cases and 66.7% (44/66) of HGIN cases; this difference was not significant. There was no difference in cellular atypia between the two groups. Interstitial fibrosis was detected more frequently in the IAC group (85.5%, 313/366 in IAC versus 0 in HGIN, P < 0.01). In biopsy specimens of IAC, a few cases showed neoplastic glands in close contact with large lymphatics, adipose tissue, and ganglion.

CONCLUSIONSIn colorectal biopsy specimen, the five features that suggest submucosal invasion of the neoplastic glands including the formation of cribriform structure, angular gland, diffuse carcinoma cells, interstitial fibrosis and neoplastic glands in close contact with the thick-walled vessels.