M/LN-eo with FGFR1 being rearranged presents most frequently as MPN with or without concomitant involvement by lymphoblastic lymphoma or acute leukemia and less like a myeloid, lymphoid, or mixed-lineage disease in the blastic phase, which can also be only extramedullary. The gene discussed is FGFR1; the disease is myeloproliferative neoplasm.