OBJECTIVETo investigate the relationship between colorectal adenocarcinoma with invasive micropapillary carcinoma (IMPC) component, lymphovascular invasion, and lymph node metastasis.

METHODSOne hundred and thirty one cases of colorectal adenocarcinoma with invasive micropapillary carcinoma component were evaluated by H&E and immunohistochemical staining. The main pathological features, percentage of IMPC component, lymphovascular invasion, and lymph node metastasis were assessed and compared to 296 cases of conventional colorectal adenocarcinoma.

RESULTSThe maximum diameter of the tumors of the IMPC group was significantly lower than the conventional group. The degree of differentiation, the lymph node metastatic rate, the average number of metastatic lymph nodes, the number of cases with lymphovascular tumor emboli were significantly higher in the IMPC group (P = 0.000). The rate of distant metastasis at operation was higher in the IMPC group (14.5%) compared to the conventional group (10.8%) even though statistical significance was not achieved (P = 0.278) . In IMPC group, as the IMPC component increased, the rate of lymph node metastasis also showed an increasing trend. The rate of lymph node metastasis were 53.0% (157/296) , 67.7% (42/62) and 85.5% (59/69) " respectively" for conventional adenocarcinoma, adenocarcinoma with ≤ 10% IMPC component and adenocarcinoma with > 10% IMPC component; the difference was statistically significant (P = 0.000).

CONCLUSIONSCompared to conventional colorectal adenocarcinomas, the colorectal carcinomas with IMPC component show a significantly higher rate of lymphovascular invasion, lymph node metastasis and distant metastasis. The percentage of IMPC component in colorectal adenocarcinoma is significantly correlated to the rate of lymph node metastasis. Therefore, presence of IMPC component and degree of tumor differentiation are predicting factors of lymph node metastasis.