Objective.To evaluate the histological features of the primary colorectal cancer tumors effecting the metastatic potential and to assess the relation of their combination to the disease prognosis.

Materials and methods. The study was performed on the surgical material of 125 primary tumors obtained from
124 patients (55 male, 69 female). The patients were operated on from November 2009 to April 2011. Statistical analysis was performed in RStudio, v.1.1.463. The histological features frequency was analyzed by chi-square and post-hoc tests. We used Kaplan — Meier curves with the log-rank test for the 10-year survival analysis. Cluster analysis was used for complex assessment of the primary tumors histological parameters.

Results. The presence of intraepithelial lymphocytes, pyogenic reaction and stroma type allowed predict the lymph node metastases presence with 68.2% sensitivity and 88.1% specificity. Cluster analysis revealed three patterns of primary tumors: infiltrative, mucinous and pyogenic. The infiltrative pattern was associated with the lower progression-free (median — 0.5 years) and tumor-specific (median — 1.3 years) 10-year survival. Patients with the mucinous pattern demonstrated longer survival time (medians — 2.3 years and 8.2 years, respectively). The most favorable clinical course was observed in the patients with the pyogenic growth type.

Conclusion. In the study, we described the histological features of the primary tumors which: a) could be assessed in the biopsy from the lesion without visible invasive margins; b) affected the prognosis; c) could be used for predicting regional metastases presence and thus, for planning the surgical treatment more precisely.