The case that finally fulfilled the criteria for an alternative diagnosis showed an aberrant karyotype with t(8;9) and the fusion gene PCM1::JAK2 was confirmed by NGS; therefore, it was finally reclassified as a myeloid/lymphoid neoplasm with JAK2 rearrangement, with a clinical picture and bone marrow biopsy compatible with MPN. The gene discussed is JAK2; the disease is myeloproliferative neoplasm.