CD34 IHC stain allows for optimal appreciation of blast cells (immature/undifferentiated blood cells) present in the bone marrow. CD34 is also used to distinguish acute leukemia and myelodysplastic syndrome (CD34-positive blasts are present) from aplastic anemia (no blasts to low CD34-positive cells present). Malignant blasts are present in acute myeloid leukemia (AML). The staining pattern for the CD34 IHC stain is membranous.
