75 Cytochemical Testing
Michelle To and Valentin Villatoro
Cytochemistry involves staining cells in vitro to visualize certain cellular components that will help determine the lineage of the cell. After staining, cells are examined microscopically.1
Myeloperoxidase (MPO)
MPO is an enzyme that is found in the primary granules of all granulocytes and monocytes and not present in lymphocytes. MPO is useful for differentiating between ALL and AML blasts.2,3
Results:2,3
Granulocytes, Myeloblasts, Auer rods: Positive
Monocytes: Negative to weak positive
Lymphocytes: Negative
Sudan Black B
Stains lipids present in the primary and secondary granules of granulocytes and monocyte lysosomes. Similar to MPO, it is useful for differentiating between AML and ALL but it is less specific.1-3
Results:1-3
Granulocytes, Myeloblasts: Positive
Monocytes: Negative to weakly positive
Lymphocytes: Negative
Nonspecific Esterases (Alpha-napthyl acetate esterase)
An enzymatic stain that is used to differentiate granulocytes from monocytes. The stain is considered nonspecific because other cells may also be stained.1-3
Results:1-3
Monocytes: Diffusely positive (Positivity can be inhibited by sodium fluoride)
Granulocytes: Negative
Lymphocytes: Negative (Except T lymphocytes which show focal positivity)
Specific Esterase (Chloroacetate esterase)
An enzymatic stain that is specific for granulocytes.1-3
Results:1-3
Granulocytes (Neutrophils), Myeloblasts, Auer rods: Positive
Monocytes: Negative to weak positive
Periodic Acid Schiff (PAS)
PAS stains glycogen related compounds.3 PAS is useful for the identification of lymphoid cells.
Results:1
Leukemic erythroblasts: Positive (normal erythroblasts are not positive)
Lymphoblasts: Block positivity
Leukocyte Alkaline Phosphatase (LAP)
LAP is an enzyme present in the secondary granules of neutrophils and not present in eosinophils or basophils. LAP is useful for distinguishing between chronic myelogenous leukemia (CML) from other conditions that show increased leukocyte counts.1
Results:1
CML: Low LAP score
Leukemoid Reactions: High LAP score
Acid Phosphatase
An enzyme that is present in the lysosomes of normal leukocytes.1
Results:1
T cell ALL: Positive
Hairy cells: Positive
Hairy cells also show positivity for tartrate resistant acid phosphatase (TRAP) whereas other cells would be inhibited by TRAP.1
Terminal Deoxynucleotidyl transferase (TdT)
TdT is a DNA polymerase found in immature cells.1 Results are useful in identifying lymphoblastic leukemias.
Results:1
Immature lymphocytes (ALL): Positive
Table 1. Cytochemistry Staining for ALL and AML Subgroups.1-5
| Acute Leukemia Subgroup | MPO | Sudan Black B | Nonspecific Esterase | Specific Esterase | PAS |
| ALL | – | – | ± | – | Block + |
| AML | + | + | – | + | ± |
| AMML | + | + | + | + | – |
| AMoL | – | ± | + | – | – |
| AEL | + | + | ± | + | + |
| AMkL | – | – | ± | + | + |
| APL | + | + | ± | + | – |
|
ALL = Acute lymphoblastic leukemia AML = Acute myeloid leukemia AMML = Acute myelomonocytic leukemia AMoL = Acute monoblastic and monocytic leukemia AEL = Acute Erythroid Leukemia AMkL = Acute megakaryoblastic leukemia APL = Acute promyelocytic leukemia |
+ = Positive – = Negative ± = Can be positive or negative |
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References:
1. McKenzie SB. Introduction to hematopoietic neoplasms. In: Clinical laboratory hematology. 3rd ed. New Jersey: Pearson; 2015. p. 424-45.
2. Roquiz W, Gandhi P, Kini AR. Acute leukemias. In: Rodak’s hematology clinical applications and principles. 5th ed. St. Louis, Missouri: Saunders; 2015. p. 543-60.
3. Gatter K, Cruz F, Braziel R. Introduction to leukemia and the acute leukemias. In: Clinical hematology and fundamentals of hemostasis. 5th ed. Philadelphia: F.A. Davis Company; 2009. p. 331-370.
4. Bentley G, Leclair SJ. Acute Myeloid Leukemias. In: Clinical laboratory hematology. 3rd ed. New Jersey: Pearson; 2015. p. 500-21.
5. Swerdlow SH, Campo E, Harris NL, Jaffe ES, Pileri SA, Stein H, et al. editors. WHO Classification of Tumours of Haematopoietic and Lymphoid Tissues Volume 2. 4th ed. International Agency for Research on Cancer (IARC); 2008.
