Prognostic and diagnostic value of endogenous erythroid colony formation in essential thrombocythemia.

Endogenous erythroid colonies (EECs), a typical characteristic of polycythemia vera (PV), could be observed in essential thrombocythemia (ET). Erythroid progenitors culture carried out in 34 previously untreated patients with unequivocal ET showed EECs in 35% of the cases. During a mean follow up of 4 years after the culture, the 12 EECs(+) and the 22 EECs(-) patients did not show any difference for a thrombotic or haemorrhagic complication, and the only one patient who showed an involvement of erythropoiesis was in the EECs(-) group.