LAUSR

Myeloid/lymphoid neoplasms with fibroblast growth factor receptor 1 (FGFR1) rearrangement are rare hematological malignancies. In the 2016 World Health Organization classification, they are listed in myeloid/lymphoid neoplasms associated with eosinophilia and rearrangement of PDGFRA, PDGFRB, or FGFR1 or with PCM1-JAK2 [1]. In these neoplasms, FGFR1 located on chromosome 8p11.2 is joined to one of 15 types of partner genes, resulting in stem cell leukemias/lymphomas [2]. These neoplasms present as myeloproliferative neoplasms (MPNs), acute myeloid leukemia (AML), and T-cell or B-cell acute lymphoblastic leukemia/lymphoblastic lymphoma (ALL/LBL) [2, 3]. Previous reports have shown a relationship between the specific partner gene of FGFR1 and the disease phenotype, such as ZMYM2-FGFR1 fusion and T-ALL [3, 4]. In general, the prognosis of myeloid/lymphoid neoplasms with FGFR1 rearrangement is very poor. Long-term remission requires timely allogeneic hematopoietic stem cell transplantation (allo-HSCT). However, early relapse after alloHSCT is a major issue [3, 5]. Recent reports have been published on two patients diagnosed with myeloid/lymphoid neoplasms with FGFR1 rearrangement, who underwent maintenance therapy to control minimal residual disease (MRD) after allo-HSCT [6, 7]. Our report details the treatment of myeloid/lymphoid neoplasms with FGFR1 rearrangement diagnosed in a third patient. He received 5azacytidine (5-AZA) maintenance therapy after allogeneic peripheral blood stem cell transplantation (allo-PBSCT) by monitoring ZMYM2-FGFR1 expression using real-time polymerase chain reaction (PCR) analysis. To our knowledge, this is the first report of successful 5-AZA therapy and tapering of immunosuppressive agents using MRD monitoring of FGFR1 rearrangement. A 38-year-old man with fever and cervical lymphadenopathy was referred to our hospital. Blood tests revealed a white blood cell count of 12.2 × 10/l (neutrophils 65%, eosinophils 9%, and no blasts), hemoglobin level of 14.3 g/dl, and platelet count of 326 × 10/l. Positron emission tomography-computed tomography showed increased fluorodeoxyglucose uptake in cervical and axillary lymph nodes bilaterally, as well as in abdominal lymph nodes. Cervical lymph node biopsy revealed increases in medium-sized atypical lymphocytes with nucleoli. Immunohistochemical staining revealed that these cells were positive for terminal deoxynucleotidyl transferase and cluster of differentiation (CD) 3. The cells were also negative for CD30, CD79a, and granzyme B, suggesting T-LBL. Lymph node cytogenetic analysis of 20 metaphases showed three normal metaphases, 17 t(8;13)(p11;q12) (Supplementary Figure 1a). Bone marrow (BM) was hypercellular with eosinophilia and without invasion by T-LBL (Supplementary Figure 1b). These findings were confirmed by flow cytometric analysis. Molecular analysis also revealed that reconstitution of the T cell receptor was negative. However, cytogenetic analysis of the BM sample showed three normal metaphases and 21 t(8;13)(p11; q12). Thus, the patient was diagnosed with myeloid/lymphoid * Seiichiro Katagiri [email protected]