We herein present an overview of the upcoming 5thedition of the World Health Organization Classification of Haematolymphoid Tumours focussing on lymphoid neoplasms. Myeloid and histiocytic neoplasms will be presented in a separate accompanying article. Besides listing the entities of the classification, we highlight and explain changes from the revised 4thedition. These include reorganization of entities by a hierarchical system as is adopted throughout the 5thedition of the WHO classification of tumours of all organ systems, modification of nomenclature for some entities, revision of diagnostic criteria or subtypes, deletion of certain entities, and introduction of new entities, as well as inclusion of tumour-like lesions, mesenchymal lesions specific to lymph node and spleen, and germline predisposition syndromes associated with the lymphoid neoplasms.
Cutaneous pseudolymphomas (PSLs) belong to a group of lymphocytic infiltrates that histopathologically and/or clinically simulate lymphomas. Different causative agents (e.g., Borrelia sp., injected substances, tattoo, arthropod bite) have been described, but in many cases no cause can be identified, hence the term idiopathic PSL. Clinicopathological correlation is important to make the diagnosis. Four main groups of cutaneous PSL can be distinguished based on histopathologic and/or clinical presentation: (a) nodular PSL; (b) pseudo‐mycosis fungoides (pseudo‐MF) and simulators of other CTCLs; (c) other PSL (representing distinct clinical entities); and (d) intravascular PSL. This article gives an overview of the histopathologic and clinical characteristics of cutaneous PSLs and proposes a new classification.