Dysplasia can affect all three lineages seen in the bone marrow. The best way to diagnose dysplasia is by morphology and special stains (PAS) used on the bone marrow aspirate and peripheral blood smear. Dysplasia in the myeloid series is defined by:
- Granulocytic series
- Hypersegmented neutrophils (also seen in Vit B12/Folate deficiency)
- Hyposegmented neutrophils (Pseudo-Pelger Huet)
- Hypogranular neutrophils or pseudo Chediak Higashi large granules
- Dimorphic granules (basophilic and eosinophilic granules) within eosinophils
- Erythroid series
- Binucleated erythroid percursors and karyorrhexis
- Erythroid nuclear budding
- Erythroid nuclear strings or internuclear bridging (also seen in congenital dyserythropoietic anemias)
- PAS (globular in vacuoles or diffuse cytoplasmic staining) within erythroid precursors in the bone marrow aspirate (has no bearing on paraffin fixed bone marrow biopsy). Note: One can see PAS vacuolar positivity in L1 and L2 blasts (AFB classification; the L1 and L2 nomenclature is not used in the WHO classification)
- Ringed sideroblasts seen on Prussian blue iron stain (10 or more iron granules encircling 1/3 or more of the nucleus and >15% ringed sideroblasts when counted amongst red cell precursors)
- Megakaryocytic series (can be the most subjective)
