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Lymphoma Polymerase Chain Reaction (PARR) 1363

antibodies, can be used to further identify Important Interspecies Differences Relative Cost: $$$$
lymphocyte populations using flow cytometry. The antibodies used in flow cytometry are a Pearls
VetBooks.ir markers are: antibodies that cross-react among several species. • Flow cytometry should be used in addition
combination of species-specific antibodies and
Examples of commonly used cell surface
to histologic and/or cytologic diagnostic
• B cell (dog) CD1, CD21, CD45RA, CD90,
Lab Artifacts
and MHC class II
• T cell (dog) CD3, CD4, CD8, and αβ-TCR Cytoplasmic fragments from fragile neoplastic techniques in the diagnosis of lymphoma,
not as a primary diagnostic test. It is not
or γδ-TCR lymphocytes can interfere with accurate quan- useful in the diagnosis and characterization
titation of cells. of lymphoid neoplasia that has mixed popula-
Causes of Abnormally High Levels tions such as T-cell rich B-cell lymphoma.
Lymphoma and lymphoid leukemia are Specimen Collection and Handling • Persistent lymphocytosis can occur in canine
associated with expansion of homogeneous Blood, bone marrow aspirates in EDTA ehrlichiosis, with expansion of CD8+ T cells.
populations of a single phenotype and size (e.g., (lavender top tube), and lymph node aspirates On the blood film, the lymphocytes show
homogeneous population of large CD21+ B in transport media or serum spiked saline. morphology consistent with large granular
cells). Overnight shipping on ice is necessary. Most lymphocytes.
laboratories request a concurrent blood film
Next Diagnostic Steps to Consider and CBC for blood and bone marrow aspirates. AUTHOR: Sharon M. Dial, DVM, PhD, DACVP
if Levels Are High Do not ship on Friday, and do not freeze the EDITOR: Lois Roth-Johnson, DVM, PhD, DACVP
See pp. 607 and 609. sample. Contact the laboratory for specific
sample and shipping needs.

Lymphoma Polymerase Chain Reaction (PARR)

Definition Causes of Abnormally High Levels prestained cytologic slide preparations can be
This test amplifies a targeted portion of the lym- Single or small number of broad amplicon submitted. Contact the laboratory for specific
phocyte DNA, the T cell and B cell receptors, bands: neoplasia sample requirements.
to determine if a population of lymphocytes
is monoclonal (likely neoplastic) or polyclonal Next Diagnostic Steps to Consider Relative Cost: $$$$
(likely reactive/nonneoplastic). if Levels Are High
Positive clonal expansion of a lymphocyte Pearls
Synonym population is diagnostic for lymphoma, war- • Tests offered by different laboratories can
Polymerase chain reaction for antigen receptor ranting lymphoma staging and treatment (pp. vary substantially in the number of gene
rearrangements (PARR) 607 and 609). sequences that are recognized by their PCR Laboratory Tests
primers. A negative clonality test does not
Physiology Important Interspecies Differences rule out neoplasia; some assays produce up
• Normal lymphocyte maturation confers a The test is dependent on DNA sequences that to 25% false-negative results.
wide range of heterogeneity to T- and B-cell are species-specific, requiring species-specific • This is an ancillary test for the identification
receptor genes. PCR primers. and characterization of lymphoma. The
• Extraction and amplification of DNA of these results of the test must be interpreted in
receptor genes via polymerase chain reac- Lab Artifacts light of histopathologic/cytologic, immuno-
tion (PCR) produces a myriad of different • Samples with a background of inflammatory histochemical, and clinical findings.
length amplification segments (amplicons) cells can mask a clonal expansion, depending • The test is most commonly used for dif-
in healthy individuals. on the specific primers used in the test. ferentiating reactive small lymphocytes
• In contrast, PCR analysis of lymphocytes that • Amplification of a sample with a small from neoplastic small lymphocytes when
have expanded monoclonally from a single number of lymphocytes can result in a microscopic morphology alone cannot
precursor cell, as in lymphoma, produces pseudoclonal PCR profile. provide a definitive diagnosis of neoplasia.
amplicons that are all of the same length.
• Occasionally, a neoplastic expansion of Specimen Collection and Handling AUTHOR: Sharon M. Dial, DVM, PhD, DACVP
EDITOR: Lois Roth-Johnson, DVM, PhD, DACVP
lymphocytes can produce a few subpopula- Fresh blood, bone marrow, body cavity fluids,
tions of neoplastic cells with slightly different lymph node aspirates, tissue, and, in some
sequences and an oligoclonal expansion. cases, formalin fixed tissues and air-dried or

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