Cun immunology is a branch of biology linked to the role of the immune system in the progression and development of cancer; The most popular application is cancer immunotherapy, in which the immune system is used to treat cancer. Cun immunosurveillance is a theory developed in 1957 by Burnet and Thomas, who suggested that lymphocytes serve as sites for the continuous detection and elimination of, mutated cells. Cancer stem cell injury appears to be an important protective mechanism that reduces cancer rates by preventing carcinogeneis and maintaining normal cellular homeostasis. It has also been suggested that vaccination has been very effective as part of the most common cancer treatment process.