Abnormal megakaryocyte morphology Megakaryocyte nucleus hyperlobulation 2017-09-02T16:40:09Z The presence of megakaryocytes in the bone marrow whose nuclei are more lobulated than expected for the size of the nucleus. A large megakaryocyte with a hyperlobulated nucleus is a cell that is larger than average size and has more nuclear lobulation than average. Some such megakaryocytes are seen in normal bone marrows but when they are present as an increased proportion they should be commented on. Increased numbers are seen sometimes in myelodysplastic syndrome but they are more frequent in myelodysplastic/myeloproliferative neoplasms (MDS/MPN) and in MPN, particularly essential thrombocythemia.