The interleukin-17 family is the key group of cytokines and displays a broad spectrum of biological functions, including regulating the inflammatory cascade in various autoimmune and inflammatory diseases, such as multiple sclerosis, neuromyelitis optica spectrum disorder, myasthenia gravis, Guillain–Barre syndrome, acute disseminated encephalomyelitis, diabetes, inflammatory skin diseases, joint inflammation, and cancer. This evidence concerns the gene IL17A and cancer.