title: The many faces of small B cell lymphomas with plasmacytic differentiation and the contribution of MYD88 testing.
abstract: Plasmacytic differentiation may occur in almost all small B cell lymphomas (SBLs), although it varies from being uniformly present (as in lymphoplasmacytic lymphoma (LPL)) to very uncommon (as in mantle cell lymphomas (MCLs)). The discovery of MYD88 L265P mutations in the vast majority of LPLs has had a major impact on the study of these lymphomas. Review of the cases contributed to the 2014 European Association for Haematopathology/Society for Hematopathology slide workshop illustrated how mutational testing has helped refine the diagnostic criteria for LPL, emphasizing the importance of identifying a clonal monotonous lymphoplasmacytic population and highlighting how LPL can still be diagnosed with extensive nodal architectural effacement, very subtle plasmacytic differentiation, follicular colonization, or uncommon phenotypes such as CD5 or CD10 expression. MYD88 L265P mutations were found in 11/11 LPL cases versus only 2 of 28 other SBLs included in its differential diagnosis. Mutational testing also helped to exclude other cases that would have been considered LPL in the past. The workshop also highlighted how plasmacytic differentiation can occur in chronic lymphocytic leukemia/small lymphocytic lymphoma, follicular lymphoma, SOX11 negative MCL, and particularly in marginal zone lymphomas, all of which can cause diagnostic confusion with LPL. The cases also highlighted the difficulty in distinguishing lymphomas with marked plasmacytic differentiation from plasma cell neoplasms. Some SBLs with plasmacytic differentiation can be associated with amyloid, other immunoglobulin deposition, or crystal-storing histiocytosis, which may obscure the underlying neoplasm. Finally, although generally indolent, LPL may transform, with the workshop cases suggesting a role for TP53 abnormalities.
authors.affiliation: Division of Hematopathology, Department of Pathology, University of Pittsburgh School of Medicine, Room G-335, 200 Lothrop Street, Pittsburgh, PA, 15213, USA. swerdlowsh@upmc.edu.
authors.forename: Steven H
authors.identifier: http://orcid.org/0000-0002-3832-3329
authors.initials: SH
authors.lastname: Swerdlow
authors.affiliation: Department of Pathology, Ankara University School of Medicine, Sihhiye, Ankara, Turkey.
authors.forename: Isinsu
authors.initials: I
authors.lastname: Kuzu
authors.affiliation: Hematopathology Service, Departments of Pathology and Laboratory Medicine, Memorial Sloan Kettering Cancer Center, New York, NY, USA.
authors.forename: Ahmet
authors.initials: A
authors.lastname: Dogan
authors.affiliation: Institute of Pathology, University Hospital Basel, Basel, Switzerland.
authors.forename: Stephan
authors.initials: S
authors.lastname: Dirnhofer
authors.affiliation: Queen Elizabeth Hospital, Hong Kong, SAR, China.
authors.forename: John K C
authors.initials: JK
authors.lastname: Chan
authors.affiliation: Department of Laboratory Medicine, Division of Pathology, Karolinska Institut and Karolinska University Hospital Huddinge, Stockholm, Sweden.
authors.forename: Birgitta
authors.initials: B
authors.lastname: Sander
authors.affiliation: Department of Clinical Pathology, Robert-Bosch-Hospital and Dr. Margarete Fischer-Bosch Institute of Clinical Pharmacology, Stuttgart, Germany.
authors.forename: German
authors.initials: G
authors.lastname: Ott
authors.affiliation: Department of Bio-Pathology, Institut Paoli-Calmettes and Aix-Marseille University, Marseille, France.
authors.forename: Luc
authors.initials: L
authors.lastname: Xerri
authors.affiliation: Institute of Pathology and Neuropathology, Eberhard Karls University of Tübingen and Comprehensive Cancer Center, University Hospital Tübingen, Tübingen, Germany.
authors.forename: Leticia
authors.initials: L
authors.lastname: Quintanilla-Martinez
authors.affiliation: Hospital Clinic, University of Barcelona, Barcelona, Spain.
authors.forename: Elias
authors.initials: E
authors.lastname: Campo
mesh_terms: D000818:Animals; D006410:Hematopoiesis / Q000235:genetics* / Q000502:physiology; D006801:Humans; D018442:Lymphoma, B-Cell, Marginal Zone / Q000175:diagnosis / Q000235:genetics* / Q000473:pathology; D008224:Lymphoma, Follicular / Q000175:diagnosis / Q000473:pathology*; D020522:Lymphoma, Mantle-Cell / Q000175:diagnosis / Q000473:pathology*; D053594:Myeloid Differentiation Factor 88 / Q000235:genetics*; D008258:Waldenstrom Macroglobulinemia / Q000175:diagnosis / Q000235:genetics* / Q000473:pathology
chemical_list: D053594:Myeloid Differentiation Factor 88
keywords: Chronic lymphocytic leukemia; Follicular lymphoma; Lymphoplasmacytic lymphoma; MYD88; Mantle cell lymphoma; Marginal zone lymphoma; Plasmacytic differentiation