In M6b, 30% or more pronormoblasts were present, with an insignificant myeloblastic component.
Erythroid maturation is left shifted with increased pronormoblasts. Pronormoblasts are intermediate in size to large, with round nuclei, fine chromatin, often prominent nucleoli, and deeply basophilic and agranular cytoplasm.
Most results with myeloid-associated antigens are negative with the exception of CD117, which can be weakly expressed in a subset of cases of the pure erythroid subtype (similar to normal pronormoblasts).
In the process of erythropoiesis, erythroid cells matures from pronormoblasts
, characterised by the loss of nucleus, condensation of chromatin to form coalescent clumps, formation of siderotic clusters, and the cessation of DNA and RNA synthesis, and optimized haemoglobin production.