Fig. 5. Summary of the relationship between immunodeficiency-associated lymphoid proliferations and lymphomas as named and defined in the revised 4^th edition of the WHO Classification (WHO-HAEM4R) and in the present 5^th edition (WHO-HAEM5).

The overarching concept applied in WHO-HAEM5 recognizes the pathological and biological similarities between proliferations presenting in various immune deficiency settings, while acknowledging their specific features. Outside the shared entities, unique proliferations are especially typical for various inborn errors of immunity (IEI). EBVMCU: EBV-positive mucocutaneous ulcer.