Megakaryocyte emperipolesis in a child with chronic neutropenia: an unusual coexistence.

The term emperipolesis defines the temporary presence of one cell within another's cytoplasm. In clinical use, megakaryocyte emperipolesis is the penetration of hematopoietic cells into the cytoplasm of megakaryocytes. The pathophysiological significance of megakaryocyte emperipolesis is uncertain. It has been described in association with neoplastic disorders, and in a few instances in idiopathic thrombocytopenic purpura, iron deficiency anemia, bleeding, and during the administration of recombinant human granulocyte colony-stimulating factor. However, megakaryocyte emperipolesis in a patient with chronic neutropenia has not been reported. In the current report, emperipolesis of hematopoietic cells within megakaryocytes in a boy with chronic neutropenia is described and the possible mechanisms are discussed.