Erythroblastic sarcoma transformation from a chronic myeloid neoplasm with FGFR1 rearrangement presenting as a pleural effusion: a case report

Myeloid/lymphoid neoplasms with FGFR1 rearrangement (MLN-FGFR1) comprise a heterogeneous group of neoplasms that can present as a myeloproliferative neoplasm, a myelodysplastic/myeloproliferative neoplasm, acute myeloid leukemia, T or B lymphoblastic leukemia/lymphoma, or mixed phenotype acute leukemia. The overall outcome of these neoplasms is poor, and these patients often show cytogenetic evolution with gain of additional chromosomal abnormalities leading to transformation to acute leukemia. Pure erythroid leukemia and erythroblastic sarcoma evolving from a preexisting chronic myeloid neoplasm have rarely been described; however, this has not been reported in MLN-FGFR1. Herein we describe a biopsy-proven chronic myeloid neoplasm with FGFR1 rearrangement with transformation to erythroblastic sarcoma presenting as a pleural effusion.