title: Autoimmune myelofibrosis: an update on morphologic features in 29 cases and review of the literature.
abstract: Autoimmune myelofibrosis (AIMF) is a distinct clinicopathological entity associated with diffuse bone marrow fibrosis and a benign clinical course. Distinction from neoplastic etiologies of marrow fibrosis, particularly primary myelofibrosis, is imperative, but few studies have documented histopathologic features in a large series. We describe 29 patients with AIMF, defined as marrow reticulin fibrosis and lymphocytic infiltration in the context of an established autoimmune disorder (secondary AIMF) or autoantibodies without a defined disorder (primary AIMF). Excluded were cases with atypical megakaryocytes, dysplasia, basophilia, osteosclerosis, unexplained splenomegaly, or neoplasms associated with myelofibrosis (MF). All cases were stained for reticulin, CD3, and CD20, with a subset additionally stained for CD138, κ, λ, immunoglobulin G (IgG), and IgG4. Lymphoid aggregates, where present, were classified into T-cell and B-cell patterns of distribution. Most patients (93%) presented with cytopenias. Sixty-nine percent (n = 20) were considered secondary AIMF and the remainder primary AIMF (n = 9). Peripheral blood showed absent-to-rare blasts and teardrop erythrocytes and absence of eosinophilia or basophilia. Characteristic bone marrow findings included hypercellularity with erythroid and megakaryocytic hyperplasias, mild reticulin fibrosis, intrasinusoidal hematopoiesis, T-cell pattern in lymphoid aggregates, mild polytypic plasmacytosis, and absence of IgG4-positive plasma cells. Primary and secondary AIMF were pathologically indistinguishable, except for an increased incidence of granulocytic hyperplasia in primary AIMF. This series confirms and expands the utility of the original diagnostic criteria for AIMF. Recognizing the characteristic morphology of AIMF and its associated clinical and laboratory features distinguishes autoimmune from neoplastic causes of MF and guides further evaluation and management.
authors.affiliation: Hematopathology Section, Department of Pathology, University of Southern California-Keck School of Medicine, Los Angeles, CA 90033. Electronic address: ria.e.vergara@gmail.com.
authors.forename: Maria E
authors.initials: ME
authors.lastname: Vergara-Lluri
authors.affiliation: The Jane Anne Nohl Division of Hematology and Center for the Study of Blood Diseases, University of Southern California-Keck School of Medicine/Norris Cancer Institute, Los Angeles, CA 90033.
authors.forename: Caroline I
authors.initials: CI
authors.lastname: Piatek
authors.affiliation: Division of Hematologic Oncology and Hematopoietic Cell Transplantation, City of Hope National Medical Center, Duarte, CA 91010.
authors.forename: Vinod
authors.initials: V
authors.lastname: Pullarkat
authors.affiliation: Hematopathology Section, Department of Pathology, University of Southern California-Keck School of Medicine, Los Angeles, CA 90033.
authors.forename: Imran N
authors.initials: IN
authors.lastname: Siddiqi
authors.affiliation: The Jane Anne Nohl Division of Hematology and Center for the Study of Blood Diseases, University of Southern California-Keck School of Medicine/Norris Cancer Institute, Los Angeles, CA 90033.
authors.forename: Casey
authors.initials: C
authors.lastname: O'Connell
authors.affiliation: The Jane Anne Nohl Division of Hematology and Center for the Study of Blood Diseases, University of Southern California-Keck School of Medicine/Norris Cancer Institute, Los Angeles, CA 90033.
authors.forename: Donald I
authors.initials: DI
authors.lastname: Feinstein
authors.affiliation: Hematopathology Section, Department of Pathology, University of Southern California-Keck School of Medicine, Los Angeles, CA 90033.
authors.forename: Russell K
authors.initials: RK
authors.lastname: Brynes
mesh_terms: D000328:Adult; D000368:Aged; D001327:Autoimmune Diseases / Q000473:pathology*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D055728:Primary Myelofibrosis / Q000473:pathology*; D055815:Young Adult
keywords: Autoimmune disorders; Autoimmune myelofibrosis; Bone marrow fibrosis; IgG4 related disease; Morphologic criteria; Non-neoplastic fibrosis