Colorectal carcinoma with a micropapillary component (MP) is an exceptionally aggressive variant, but has never been investigated in terms of survival analysis. Thirty colorectal carcinomas with a MP were identified from a series of 221 colorectal carcinomas. Carcinomas with and without a MP were compared in terms of histologic and immunohistochemical markers. Colorectal carcinoma with a MP seemed to have a lower differentiation status, increased tumor budding, more frequent lymphovascular and perineural invasion, more frequent lymph node metastasis, higher tumor node metastasis (TNM) stage, and less nuclear beta-catenin staining (P<0.05). Further analysis revealed that the presence of a MP predicted more frequent lymph node metastasis in T1 and T2 stages but not in T3 and T4 stages. Five-year survival rates for patients with a MP and those without were 50% and 73%, respectively. Furthermore, in TNM stages I and II, but not in TNM stages III and IV, a MP was an unfavorable prognostic variable. A MP was demonstrated to be an independent unfavorable prognostic indicator in TNM stages I and II by the multivariate Cox proportional hazard model. Colorectal carcinoma with a MP should be distinguished from colorectal carcinoma of conventional histologic type.

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