Plasma Cell Tumors in Hematological Classifications of 2022: WHO-HAEM5 (WHO, 5th edition) and ICC (International Consensus Classification). A Clinician’s View

Abstract

In 2022, the hematological community was faced with a rather non-trivial event of simultaneous publication of two competitive classifications of hematopoietic and lymphoid tumors drawn up by different teams of the international leading experts. During the last 20 years, the generally recognized standard used for diagnosis was provided by several consecutive editions of classifications of hematological neoplasms published by the World Health Organization (WHO) in 2001, 2008, and 2016. Since the 4th edition of the WHO classification (WHO-HAEM4), new clinicopathologic, biological, and molecular knowledge has accumulated in this area, which promoted the refinement of diagnostic criteria for some diseases, the emergence of new terms, and the endorsement of notions previously defined as requiring further clarification. As a result, the next 5th edition of the WHO classification of tumours of haematopoietic and lymphoid tissues (WHO-HAEM5) was prepared and published as a preliminary article in the Leukemia. In this regard, it is worth noting that the final version of the WHO Blue Book was not released in 2023 and, therefore, can still be accomplished by some additions. Furthermore, in the same year of 2022, the Blood published the article “The International Consensus Classification of Mature Lymphoid Neoplasms” abbreviated to ICC. The authors of the two classifications hardly overlap. The present review compares these classifications with regard to new diagnostic criteria and verification of concrete clinicopathologic categories. The review largely focuses on plasma cell tumors and related B-cell lymphoproliferative diseases characterized by monoclonal immunoglobulin secretion.