The more common variant, referred to as erythremic myelosis, and subsequently as erythroleukemia and erythroid/myeloid leukemia by others, is composed of immature erythroid and myeloid elements.
Because of the extreme rarity of the pure erythroid leukemia subtype, this review is heavily biased toward the erythroleukemia subtype of AEL.
Other than the de novo and familial categories of disease, in our view, many of the cases of secondary AEL (usually designated as erythroleukemia or AML-M6 in the literature) should be viewed with skepticism.
In the erythroleukemia subtype, maturation of erythroid precursors is often left shifted and dysplasia is identified in all maturation stages.
Dysplasia of megakaryocytes often can be appreciated in the erythroleukemia subtype, whereas the neoplasm can appear completely undifferentiated in cases of the pure erythroid leukemia subtype (Figure 3, B).
In both the erythroleukemia and pure erythroid leukemia subtypes, erythroblasts are often highlighted by the periodic acid-Schiff (PAS) reaction in either a globular or diffuse pattern, with the diffuse pattern occurring in more mature erythroblasts (Figure 3, C).
The myeloblasts of the erythroleukemia subtype express myeloid-associated markers including CD13, CD33, CD117 (KIT), and MPO, with or without expression of CD34 and HLA-DR.
Blasts in the erythroleukemia type of AEL can be positive for lysozyme or CD68.
Most cytogenetic data available for AEL cases are derived from conventional cytogenetic analysis of the most common subtype, erythroleukemia.
22,23) Rare cases of erythroleukemia with der(1;7)(q10;p10) have been reported, especially in East Asian individuals.
Although we have no doubt that cytogenetic abnormalities correlate with prognosis, as has been shown in many studies of AML in general, the spectrum and types of the reported cytogenetic abnormalities in cases classified previously as erythroleukemia suggest that this "entity" has been highly heterogeneous.