CD34 and CD79a immunopositivity in megakaryocytes

CD34 and CD79a are markers of hematopoietic stem cell and B-lymphoid cells, respectively. The abnormal expression of these markers in megakaryocytes has been noticed in cases of myelodysplastic syndrome, inherited platelet disorders, and reactive erythrocytosis. As a routine practice, while studying post-induction chemotherapy marrows in acute leukemia, immunomarkers, positive in the initial diagnostic workup, were performed to look for the residual blasts. Interestingly, we noticed CD34 immunopositive megakaryocytes in four such cases. CD79a positive megakaryocytes were also seen in five other cases of post-induction acute lymphoblastic leukemia. All these megakaryocytes, which were regenerating and in clusters, showed both topographic and cytological features of dysmegakaryopoiesis. CD 34 and CD79a, which are often used to monitor residual disease in the post-chemotherapy bone marrow, show aberrant positivity in the megakaryocytes. This novel finding of regenerating megakaryocytes may be used as a feature of dysmegakaryopoiesis in megakaryocytes.