Cytochemical Stains in Hematology
Cytochemical stains are special stains used for staining peripheral blood and bone marrow smears that help in classifying and differentiating different types of leukemias. In resource poor countries, role of special stains cannot be ignored as they are cheap, time saving, easy to perform, yet effective tools in differentiating different types of leukemias.
Cytochemical stains are enzymatic colorimetric reactions that occur in the cells of interest, and reveal the presence or absence of certain cellular components that characterize different hematopoietic lineages. The most common cytochemical stains used in hematology are:
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Leukocyte Alkaline Phosphatase (LAP): This stain detects the alkaline phosphatase activity in the cytoplasm of neutrophils, eosinophils, osteoblasts, B lymphocytes and endothelial cells. It helps in differentiating chronic myeloid leukemia (CML) from leukemoid reaction, as LAP score is low in CML and high in leukemoid reaction.
Myeloperoxidase (MPO): This stain detects the presence of myeloperoxidase enzyme in the primary granules of myeloid cells. It is positive in most cases of acute myeloid leukemia (AML) and negative in acute lymphoblastic leukemia (ALL).
Sudan Black B (SBB): This stain detects the presence of lipids in the granules of myeloid cells. It is similar to MPO stain, but more sensitive and less specific.
Chloroacetate Esterase (CAE): This stain detects the presence of esterase enzyme in the granules of myeloid cells. It is positive in granulocytic and monocytic cells, and negative in lymphoid cells.
Nonspecific Esterase (NSE): This stain detects the presence of esterase enzyme in the cytoplasm of monocytes and megakaryocytes. It is positive in monocytic and megakaryocytic cells, and negative in granulocytic and lymphoid cells.
Acid Phosphatase (AP): This stain detects the presence of acid phosphatase enzyme in the lysosomes of cells. It is positive in T lymphocytes and hairy cell leukemia, and negative in B lymphocytes and other leukemias.
Periodic Acid Schiff (PAS): This stain detects the presence of glycogen and other carbohydrates in the cytoplasm of cells. It is positive in B lymphoblasts, erythroid precursors, megakaryocytes and some cases of AML, and negative in T lymphoblasts and most cases of ALL.
Cytochemical stains are useful adjunct assays for the proper classification of acute leukemia, especially when immunophenotyping and cytogenetic analysis are not available or inconclusive. However, they have some limitations, such as variability in staining intensity, overlapping results among different subtypes, and interference by drugs or storage conditions. Therefore, cytochemical stains should be interpreted along with morphological features and clinical findings to reach a definitive diagnosis.
If you want to learn more about cytochemical stains in hematology, you can download some PDF files from these links:
[Cytochemical Staining - Springer]
[Cytochemical Stains in Haematology - Journal of Evidence-Based Medicine ...]
[Cytochemical Staining SpringerLink]