[Emperipolesis in megakaryocytes in patients with thrombocytosis in the course of myeloproliferative disorders].

The incorporation of other marrow cells into megakaryocytes, termed emperipolesis, has been studied in paraffin biopsy sections from 17 untreated patients with myeloproliferative disorders (MPDs). The group consisted of 12 females and 5 males, aged from 34 to 72 years (mean 51.3). Patients with essential thrombocythemia (ET)--9, chronic granulocytic leukemia (CGL)--4, polycythemia vera (PV)--3, and myelofibrosis (MF)--1 were included into the study. Clusters of large polyploid megakaryocytes were observed in anatomic relation to the marrow sinusoidal system. Emperipolesis has been scored as being present or absent per 100 megakaryocytes/slide. Cells found within megakaryocytes were mostly erythroblasts and mature granulocytes. The number of incorporated cells varied from 1 to 7 per one megakaryocyte. Considering the 17 patients with MPDs, emperipolesis was observed in a vast majority of those with ET(8/9) and PV(2/3), in some with CGL(1/4), but not in MF. The mechanism of megakaryocytic emperipolesis remains unclear. Adhesion molecules on megakaryocytes and incorporated cells may possible mediate the cell-to-cell interactions important for emperipolesis.