Hematopathology Laboratory
Cytochemical Stains
Cytochemical stains are performed on liquid or tissue specimens. The laboratory director will issue a written report and interpretation.
Myeloperoxidase (MPO)
The myeloperoxidase stain is positive in cells of the granulocyte series. Occasionally, cells in the monocyte series will have a few positive granules, but lymphoid cells are negative. Myeloperoxidase activity increases as myeloid cells mature, so very immature myeloid blasts will have absent to weak staining. This stain is part of the routine cytochemical stain panel for the diagnosis of acute leukemia.
Specimen requirements: Unstained peripheral blood or bone marrow aspirate smears, anticoagulated peripheral blood or bone marrow, other body fluids
Non-specific Esterase (NSE)
The non-specific esterase stain used in our laboratory is for a-naphthyl butyrate esterase. This stain is positive in cells from the monocyte and megakaryocyte series. Lymphocytes may stain focally and occasionally myeloid cells will stain very weakly. This stain is most commonly used for the diagnosis of acute myelogenous leukemias with monocytic differentiation (FAB types M4 and M5). This stain is part of the routine cytochemical stain panel for the diagnosis of acute leukemia.
Specimen requirements: Unstained peripheral blood or bone marrow aspirate smears, anticoagulated peripheral blood or bone marrow, other body fluids
Periodic acid-Schiff (PAS)
The periodic acid-Schiff stain reacts with carbohydrates and glycoproteins. Mature granulocytes and monocytes stain with a diffuse cytoplasmic pattern. Platelets usually stain with a coarsely granular pattern. Lymphocytes are generally negative or may have a few positive cytoplasmic granules. The lymphoblasts in approximately 50% of ALL leukemias contain coarse PAS-positive granules in a "string of pearls" pattern around the nucleus. Increased amounts of "chunky" PAS-positive material are also seen in the abnormal erythroblasts in erythroleukemia (FAB type M6). Sézary cells are sometimes positive for PAS also. Because of its limited utility in the diagnosis of acute leukemia, this stain is not part of the routine panel used for the diagnosis of acute leukemia, but is performed in cases where it is thought to be useful or when requested.
Specimen requirements: Unstained peripheral blood or bone marrow aspirate smears, anticoagulated peripheral blood or bone marrow, other body fluids
Tartrate-resistant Acid Phosphatase (TRAP)
Acid phosphatase exists as five isoenzymes. While acid phosphatase is present in almost all leukocytes, isoenzyme 5 is restricted to the cells of hairy cell leukemia as well as some other non-hematopoietic tissues. It is distinguished by its inability to be inhibited by tartaric acid. The neoplastic cells in hairy cell leukemia will stain strongly positive for acid phosphatase in the presence of tartrate.
Specimen requirements: Unstained peripheral blood or bone marrow aspirate smears, anticoagulated peripheral blood or bone marrow, other body fluids
Leukocyte Alkaline Phosphatase (LAP)
The leukocyte alkaline phosphatase (LAP) stain will stain cells in the myeloid series. The LAP stain may be performed on liquid or tissue specimens, but is most commonly performed on peripheral blood specimens. One hundred neutrophils are counted and a score between 0 and 4 is assigned to each cell based on the amount of staining present, with "0" representing no staining and "4" heavy staining. The scores are then totaled. Normal peripheral blood scores are 60-140. Scores are elevated in leukemoid reactions, normal to elevated in agnogenic myeloid metaplasia with myelofibrosis, normal in polycythemia vera, and decreased in paroxysmal nocturnal hemoglobinuria, acute myelogenous leukemia, and chronic myelogenous leukemia.
Specimen requirements: Unstained peripheral blood smears, heparin anticoagulated peripheral blood (EDTA is inhibitory for the LAP reaction)
Chloroacetate Esterase (CAE)
The chloroacetate esterase stain (CAE) stain is positive in myeloid cells. It is more specific than the myeloperoxidase stain but not as sensitive. For that reason we do not usually recommend the CAE for differentiating acute leukemias. The CAE stain may be performed on formalin fixed, paraffin embedded specimens and may be useful in the diagnosis of granulocytic sarcoma (chloroma).
Specimen requirements: Unstained peripheral blood or bone marrow aspirate smears, anticoagulated peripheral blood or bone marrow, other body fluids, tissue specimens including fresh, frozen, or fixed/paraffin embedded.
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Last updated: 6/22/00
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