title: Plasmacytoid dendritic cell proliferations and neoplasms involving the bone marrow : Summary of the workshop cases submitted to the 18th Meeting of the European Association for Haematopathology (EAHP) organized by the European Bone Marrow Working Group, Basel 2016.
abstract: Two distinct forms of neoplasms derived from plasmacytoid dendritic cells (PDC) exist: mature PDC proliferations associated with myeloid neoplasms and blastic PDC neoplasms (BPDCN). Ten cases of PDC proliferations and neoplasms in the bone marrow have been submitted to the bone marrow workshop held at the 18th EAHP meeting. Based on observations from the submitted cases, scattered PDC (≤1% of cells) and PDC aggregates (≤10 PDC/HPF) reflect the normal bone marrow composition, while in myelodysplastic syndromes (MDS), there is a propensity for larger/more PDC aggregates (1-5% and 35 PDC/HPF). A shared PTPN11 mutation between a mature PDC proliferation and an accompanying MDS provides evidence of clonal relationship in such instances and shows that PDC are a part of the malignant clone. CD123 and CD303 should be considered backbone markers to histopathologically establish the diagnosis of BPDCN, since they are detectable in almost all cases and properly well on biopsies subjected to different fixations. Expression of some T-cell markers (e.g., CD2 and CD7 but not CD3), B-cell markers (e.g., CD79a but not CD19 and CD20), and myeloid markers (e.g., CD33 and CD117 but not myeloperoxidase) can be observed in BPDCN. Genetical data of the summarized cases corroborate the important role of chromosomal losses in BPDCN. Together with five previously reported instances, one additional workshop case with MYC rearrangement proposes that translocations of MYC may be recurrent. The frequent nature of deleterious mutations of IKZF3 and deletions of IKZF1 suggests a role for the Ikaros family proteins in BPDCN.
authors.affiliation: Institute of Pathology, University of Basel, Schönbeinstrasse 40, 4031, Basel, Switzerland. alexandar.tzankov@usb.ch.
authors.forename: Alexandar
authors.identifier: http://orcid.org/0000-0002-1100-3819
authors.initials: A
authors.lastname: Tzankov
authors.affiliation: Department of Pathology, Radboud University Medical Center, 824, 6500 HB, Nijmegen, Netherlands.
authors.forename: Konnie
authors.initials: K
authors.lastname: Hebeda
authors.affiliation: Pathology, Städtisches Klinikum München, Sanatoriumsplatz 2, 81545, Munich, Germany.
authors.forename: Markus
authors.initials: M
authors.lastname: Kremer
authors.affiliation: Department of Pathology, University Medical Center Utrecht, H04-312, POB 85500, 3508 GA, Utrecht, Netherlands.
authors.forename: Roos
authors.initials: R
authors.lastname: Leguit
authors.affiliation: Division of Hematopathology, Department of Pathology and Laboratory Medicine, Weill Medical College of Cornell University, 525 E, 68th Street, New York, 10021, USA.
authors.forename: Attilio
authors.initials: A
authors.lastname: Orazi
authors.affiliation: Department of Histopathology, Guy's and St Thomas' Hospital, Westminster Bridge Road, London, SE1 7EH, UK.
authors.forename: Jon
authors.initials: J
authors.lastname: van der Walt
authors.affiliation: Pathology Unit, Department of Pathophysiology and Transplantation, University of Milan and Fondazione IRCCS, Ca' Granda - Maggiore Policlinico, Via Francesco Sforza 35, 20122, Milan, Italy.
authors.forename: Umberto
authors.initials: U
authors.lastname: Gianelli
mesh_terms: D001706:Biopsy; D001853:Bone Marrow / Q000378:metabolism / Q000473:pathology*; D049109:Cell Proliferation; D003713:Dendritic Cells / Q000473:pathology*; D014644:Genetic Variation; D023281:Genomics / Q000379:methods; D015620:Histiocytic Disorders, Malignant / Q000175:diagnosis* / Q000209:etiology / Q000401:mortality / Q000628:therapy; D006801:Humans; D060787:Neoplasm Grading; D010641:Phenotype; D012008:Recurrence
keywords: BCL2; BPCDN; Bone marrow biopsy; CD123; CD303; EAHP workshop; Ikaros; MYC; Neoplasm; PTPN11; Plasmacytoid dendritic cells