Neutrophils are one of the key barriers to anti-infective protection, an important mechanism of which is NETosis - the formation of neutrophil extracellular traps (NET). In recent years, this ambiguous biological phenomenon has been considered as a factor of unfavorable prognosis in some types of cancer. This review is devoted to the analysis of the role of NETosis in the pathogenesis of autoimmune diseases and other non-communicable diseases. The role of NET in malignant tumors, in particular in metastasis and progression of the tumor process, has been studied and data on the subpopulations of neutrophils – low-density neutrophils (LDN) and high-density neutrophils (HDN) in tumor processes have been analyzed. Further study of the phenomenon of netosis and the characteristics of peripheral blood neutrophils in cancer patients will be useful both for detailing the mechanisms of the metastatic cascade and for identifying their role as a biomarker and a possible therapeutic target.