Introduction

The “8p11 myeloproliferative syndrome” (EMS) is an extremely rare hematological malignancy characterized by disruption and constitutive activation of fibroblast growth-factor receptor type 1 (FGFR1; 1). The disease is also referred to as “stem-cell leukemia/lymphoma syndrome” (SCLL) or “myeloid and lymphoid neoplasms with FGFR1 abnormalities” (ICD-O code 9967/3; 2,3). Clinically, EMS is typically a biphenotypic disorder that may present as a myeloproliferative neoplasm, acute leukemia or lymphoblastic lymphoma, usually in conjunction with prominent eosinophilia. Although uncommon, EMS is of interest because of its stem-cell origin, marked genotype/phenotype correlations and diverse range of FGFR1 fusions, which all demonstrate a common pathogenic mechanism. Cell-line and animal studies have dissected the signaling pathways that are critical for transformation and may ultimately lead to molecularly targeted therapy.

Clinical features

Clinical and laboratory descriptions of more than 40 cases of EMS have been published and, although the clinical course is highly variable, some common features have emerged, as summarized in Table 75.1. The age range at onset is between 5 months and 84 years, with a median of 32 and a slight male to female predominance of 1.5:1. EMS may present as a myeloid and/or lymphoid malignancy; the myeloid presentation may be either a myeloproliferative neoplasm (MPN) or acute myeloid leukemia (AML), and the lymphoid presentation is typically either B-cell acute lymphoblastic leukemia (B-ALL) or T-cell lymphoblastic lymphoma (T-LBL).