Summary Recent studies suggest that immune-classification (immunoscore) in cancer patients has a prognostic value in some cases that seems to be superior to the AJCC/ UICC TNM classification. The clinical outcome can vary significantly among patients with a particular diagnosis within the same TNM stage. Immunoscore methodology quantifies and detects different types of immune cells in tumor tissue, and also determines the density of their infiltration and localization at the tumor site. Currently within an international collaboration of 23 centers in 17 countries (including our department), immunoscore is being evaluated in more than 7,000 colorectal cancer patients in terms of the tumor microenvironment, focusing on the presence of immune cells both in the tumor tissue and the tumor invasive margin. Immunoscore results are assessed in correlation with: 1. patient‘s response to the treatment, 2. rate of progression, disease prognosis and other immune parameters. It appears that the TNM classification and tumor invasiveness is statistically dependent on the immune response of the patient (there is an inverse correlation between the density of the infiltration of CD 8+, CD3+ lymphocytes and the tumor stage). High densities of T-lymphocytes (CD8+, CD3+) both in the core and the invasive margin of the primary tumor are associated with longer-term asymp tomatic survival, overall survival, lower risk of relapse and reduced likelihood of metastases. The project of the international collaboration aims to introduce immunoscore in routine diagnostics.