ACE2 and susceptibility to pneumonia measurement: “Coronavirus,” “ACE2,” “SARS coronavirus,” “pneumonia,” “cytokine storm,” and “neutrophil to lymphocyte ratio” are all related to COVID-19, while “circulating tumor cell,” “prevalence,” and “cancer” are all associated with cancer, indicating that the role and mechanism of NETosis in COVID-19 and cancer are at the forefront of research in this field, which is accordance with the results of co-citation reference analysis.