The ESID 2019 Meeting in Brussels will be a unique meeting, focusing on the fascinating and important intertwinement between primary immunodeficiencies, infections and malignancy. We have selected the very best, internationally distinguished speakers to cover this field. Topics include PIDs with a well-known increased risk of malignancy, (such as DNA repair disorders, CVID, T cell deficiencies) the impact of viral infections on the development of malignancies, the immunology of the tumor microenvironment and much, much more. Issues regarding pathogenesis, diagnosis, treatment and screening will be approached from different viewpoints.