**Abstract**

Colorectal cancer (CRC) is the third most commonly diagnosed malignancy and the fourth leading cause of cancer death in the world, accounting for about 1.4 million new cases and almost 700,000 deaths in 2012. The clinical outcome and the tumor progression are now considered the result of a balance between the invasiveness of the tumor and the immune response of the patient against the tumor. The immune system has the ability to control and shape cancer through a mechanism called immunoediting, which include elimination, equilibrium, and escape. The consensus Immunoscore is a scoring system that outlines the density of CD3+ and CD8+ T-cell effectors existent in the tumor and its invasive margin. The pre-existing intra-tumoral immunity could be enhanced and activated by immunotherapy. Immunoscore could be a good prognostic marker, by identifying patients at high risk of tumor recurrence and stratifying patients who could benefit from adjuvant therapies. Human surfaces and cavities are populated by numerous microbial communities, and they play an indispensable role in human health, as they interact with the immune system. The authors made a literature revision concerning the role of Immunoscore and microbiome in colorectal cancer.

**Keywords:** colorectal cancer, Immunoscore, microbiome, diet, CD3+ T cell, CD8+ T cell
