System of organism defense is an important complex of interrelated cellular, molecular, genetic, and other components, which regulate homeostasis of host. Experimental and clinical data show that immune system functions are significant, but also a complicated question in cancer development. It is very important to investigate and understood how immune system coordinates the response to cancer cells. Our understanding about innate and adaptive immunity functions and interaction with transformed cells is constantly changing. Different responses of these system components can promote, reduce, or inhibit tumor development. It is established that malignant cells develop into invasive cancer with interaction with tumor microenvironment, which is influenced by inflammation. Clinical and experimental studies have revealed the link between inflammation and cancer risk. Many cancers develop in the sites of inflammation. Activation of humoral and cellular immunity may predispose to neoplastic or cancer development. Despite the scientific progress, understanding of the immune system mechanisms responding to malignance remains insufficient.