Increased multinucleated megakaryocytes as an isolated finding in bone marrow a rare finding and its Clinical significance

Objectives: Multinucleated megakaryocytes are a unique morphologic form of megakaryocytes characterized by multiple, distinctly separated nuclei. We investigated whether increased multinucleated megakaryocytes (≥25%) in otherwise normal-appearing bone marrow were associated with the development of a myelodysplastic syndrome (MDS). Methods: We retrospectively reviewed the medical records and bone marrow biopsy specimens of patients evaluated at our institution from 2011 to 2015 that met all of the following criteria: (1) 25% or more multinucleated megakaryocytes, (2) no other dysplastic features, (3) absence of a myeloid neoplasm, and (4) absence of neoplastic karyotypic abnormalities. Results: Nine cases of 19,885 bone marrow biopsy specimens were identified. The indications for bone marrow examination included plasma cell neoplasm, lymphoma, and cytopenia(s). All patients had anemia at the time the multinucleated megakaryocytes were found. No patients had thrombocytopenia or neoplastic karyotypic abnormalities. Follow-up was available for seven patients with a median of 27 months (range, 7-53 months). No patients developed progressive cytopenias or MDS. Conclusions: Multinucleated megakaryocytes (≥25%) as an isolated finding in the bone marrow are a rare phenomenon. These patients do not appear to be at increased risk of developing progressive cytopenia(s) or MDS. Caution should be taken to not overdiagnose these cases as MDS.