Name the cytochemical stains that are typically used in the workup of the following and how they are used to differentiate these conditions:

a. AML-myelomonocytic
b. APL
c. ALL
d. AML-Monoblastic
e. AML-Erythroid

What will be an ideal response?

Answer: MPO is used to differentiate AML from ALL. It stains primary granules that are present only in myeloid cells. AML subtypes are positive and ALL subtypes are negative with this.
SBB is also used to differentiate AML from ALL. It stains neutral fats. AML subtypes are positive and ALL subtypes stain negative with SBB.
Nonspecific esterase (NSE) differentiates myeloid subtypes of AML from monocytic subtypes of AML. The esterase used as a substrate is commonly found in dividing monocytic cells, so monocytic dividing cells stain positive, whereas myeloid cells stain negative.
Specific esterase also differentiates myeloid and monocytic subtypes, and gives reverse reactions compared to NSE. The esterase used as a substrate is commonly found in myeloid cells; thus, myeloid cells stain positive, whereas monocytic cells stain negative.
Periodic acid Schiff stain is used to differentiate ALL from the erythroid subtype of AML. PAS stains glycogen, which is found in varying concentrations in all nucleated cells. Consequently, both stain positive, but the pattern determines lineage. Lymphoid cells have coarse block reactivity with PAS stain, whereas erythroid cells have a coarse granular reactivity with PAS stain.