Introduction

The 2008 World Health Organization (WHO) classification system for hematologic malignancies uses histology and genetic information to organize myeloid neoplasms into five operational categories: acute myeloid leukemia (AML), myelodysplastic syndromes (MDS), myeloproliferative neoplasms (MPN), “MDS/MPN,” and “myeloid/lymphoid neoplasms associated with eosinophilia and rearrangements of platelet-derived growth factor receptor α/β or fibroblast growth factor receptor 1” (Table 9.1). The MPN category is in turn subclassified into eight separate entities: chronic myelogenous leukemia (CML), polycythemia vera (PV), essential thrombocythemia (ET), primary myelofibrosis (PMF), systemic mastocytosis (SM), chronic eosinophilic leukemia, not otherwise specified (CEL-NOS), chronic neutrophilic leukemia, and “MPN, unclassifiable.” The first four are referred to as “classic” MPN and further subclassified into BCR-ABL-positive (CML) and BCR-ABL-negative classic MPN. This chapter will focus on the latter.

Historical perspective

In 1951, William Dameshek (1900–69) grouped the four classic MPN (CML, PV, ET, and PMF), along with DiGuglielmo's syndrome (erythroleukemia), under the rubric of “myeloproliferative disorders (MPD).” However, the history of MPD antedates Dameshek by more than a century. In 1879, Gustav Heuck (1854–1940) described PMF under the title of “Two cases of leukemia with peculiar blood and bone marrow findings.” In 1904, Max Askanazy (1865–1940) reported another PMF case with substantial EMH of the liver and diffuse bone marrow fibrosis. In 1907, Herbert Assmann (1882–1950) described a similar case (“Heuck–Assmann syndrome”), which he called “osteosclerotic anemia.”