Are microproerythroblasts in human bone marrow real or artefacts? A cytochemical note

Summary erythroid precursors were studied in human bone marrow smears to provide more information on small proerythroblasts – “microproerythroblasts” – using a silver reaction to demonstrate silver stained nucleolar organizer regions (AgNORs) and light microscopic densitometry of large irregularly shaped nucleoli and cytoplasm stained for RNA. No significant differences were found for the density of such nucleoli and basophilic cytoplasm between characteristic large proerythroblasts with a nuclear diameter larger that 9 μm (K2 and K1 erythroblasts) and small proerythroblasts – “microproerythroblasts” representing a subpopulation of K1/2 erythroblasts (early basophilic erythroblasts), which are characterized by a smaller nuclear diameter. In addition, large irregularly shaped nucleoli of “microproerythroblasts” possessed numerous silver stained particles representing AgNORs similar to those of large proerythroblasts. The number of AgNORs in “microproerythroblasts” was slightly, but significantly, smaller than that in large characteristic proerythroblasts.