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Clinical Pathology Laboratory - Available Test
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Cytochemistry
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| Cytochemistry involves staining the enzyme content of cells in
blood and/or bone marrow to identify their lineage. The cytochemistry
is done by Dr. Blue, who is an expert in the field of leukemia. She
uses several cytochemical stains, including non-specific esterase
(NSE), alkaline phosphatase, chloroacetate esterase and peroxidase.
The staining qualities of each cell lineage differ depending on the
species. In general, lymphocytes and erythroid cells from all species
do not stain with any of these enzymes (certain lymphoid cells can
display focal cytoplasmic NSE staining). In dogs, alkaline phosphatase
and NSE are markers of monoblasts and monocytes, respectively. In
contrast, both peroxidase and chloroacetate esterase identify cells
of granulocytic lineage. |
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| Cytochemistry is used for the classification of acute leukemias.
These leukemias arise in the bone marrow and replace the normal hematopoietic
tissue. Most cases present with large numbers of circulating blasts,
although a few animals can be pancytopenic with no circulating blasts.
The blasts cannot be identified as to their lineage on the basis of
their morphologic characteristics in routine blood and bone marrow
stains (Wrights-based stains), i.e. they could be lymphoid or myeloid
in origin. Indeed, in many cases, the blasts are erroneously identified
as being lymphoid (myeloid leukemias are more common than lymphoid
leukemias in animals). Therefore, further techniques are required
to identify the cell lineage. It is generally believed that myeloid
leukemias have a poorer prognosis compared to lymphoid leukemias,
therefore classification of the type of leukemia is important. The
techniques used to identify cell lineage include flow cytometry (using
monoclonal antibodies against cell-specific markers) and cytochemistry.
Here at Cornell, we currently only offer cytochemical staining. This
should always be done in conjunction with a morphologic assessment
of the bone marrow using Wright's stains (i.e. bone marrow cytology).
In general, in leukemias, bone marrow is the preferred sample, together
with venous blood. However, if there are large numbers of circulating
blasts, venous blood samples can be used for classification by cytochemistry.
Note that dogs with lymphoma can have circulating lymphoblasts. This
is called a lymphoma cell leukemia. In some cases, lymphoblasts can
be seen in high numbers in peripheral blood (especially in canine
hepatosplenic lymphomas). In these cases, marrow may not be infiltrated
and bone marrow cytology should be first before cytochemical evaluation
to identify cell lineage. |
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Bone marrow from a cat with acute leukemia (the Wright's stained
smear of this cat's marrow can be seen under our bone marrow report).
The blasts have diffuse cytoplasmic positive staining for NSE (arrows),
identifying them as monoblasts. The diagnosis in this case was acute
monoblastic leukemia. |
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