Page 1346 - Small Animal Internal Medicine, 6th Edition

1318 PART XII Oncology

lymphocyte count of 100,000/µL most certainly has CLL and
WBC Run not an infectious disease), anemia and thrombocytopenia
VetBooks.ir occur in approximately half of the dogs. Although cytologic
evaluation of bone marrow aspirates in dogs with CLL
usually reveals the presence of many morphologically normal
lymphocytes, normal numbers of lymphocytes are occasion-
ally detected. This is probably because the lymphocytosis in
Fluorescence of recirculation rather than from the increased clonal prolif-
some animals with CLL, as in people, stems from disorders

eration of lymphocytes in the bone marrow. As in dogs with
acute leukemias, in dogs with high-count CLL the neoplastic
cells may be counted as reticulocytes by flow cytometry-
based analyzers.
Monoclonal gammopathies have been reported in
approximately two thirds of dogs with CLL in which serum
was evaluated using protein electrophoresis. The monoclonal
component is usually immunoglobulin M (IgM), but IgA
Granularity and IgG components have also been reported. This mono-
A NEU LYM MONO EOS BASO URBC clonal gammopathy can lead to hyperviscosity. Rarely, dogs
with CLL have paraneoplastic, immune-mediated blood
WBC Run disorders (e.g., hemolytic anemia, thrombocytopenia, neu-
tropenia). However, in our experience, monoclonal gam-
mopathies are uncommon in dogs with CLL.
The hematologic features of CML in dogs are poorly char-
acterized but include leukocytosis with a left-shift down to
myelocytes (or occasionally myeloblasts), anemia, and pos-
sibly thrombocytopenia, although thrombocytosis can also
Fluorescence occur. The hematologic findings seen during a blast crisis are
indistinguishable from those seen in dogs with AML or ALL.

Diagnosis
Absolute lymphocytosis is the major diagnostic criterion for
CLL in dogs. Although other diseases (e.g., ehrlichiosis,
babesiosis, leishmaniasis, Chagas disease, Addison disease)
should be considered in the differential diagnosis of dogs
with mild lymphocytosis (i.e., 7000-20,000/µL), marked
Granularity lymphocytosis (i.e., more than 20,000/µL) is almost pathog-
B NEU LYM MONO EOS BASO URBC nomonic for CLL. If the physical examination and hemato-
logic abnormalities discussed in previous paragraphs (i.e.,
FIG 80.6 mild lymphadenopathy, splenomegaly, monoclonal gam-
White blood cell dot plot from a ProCyte Dx in the dog mopathy, anemia) are found, this may help establish a diag-
with chronic lymphocytic leukemia depicted in Fig. 80.5 nosis of CLL in dogs with lymphocytosis, although all these
(A) compared with a normal dot plot (B). Note the larger, changes can also be present in dogs with chronic ehrlichiosis
denser lymphocyte cloud in blue (A), positioned in the same (see Chapter 93). The phenotypic distribution after perform-
location as that in normal dogs (B), suggesting that they are ing immunophenotyping may also establish if the cell
mature, well-differentiated lymphocytes. The straight line population is monoclonal or polyclonal. In patients with
between the lymphocyte and monocyte clouds indicates that
the instrument is “having trouble” differentiating some of the lymphocytosis in which a confirmatory diagnosis of CLL
neoplastic cells from normal monocytes. The numeric values cannot be made, a polymerase chain reaction (PCR) assay
in this dog consisted of marked leukocytosis (53 × 10 /L), for clonality (PARR) will typically reveal if the cells are clonal
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marked lymphocytosis (39.2 × 10 /L), moderate monocytosis in origin.
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(3.2 × 10 /L), and moderate thrombocytopenia (84 × 10 /L). The diagnosis of CML may be challenging, particularly
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because this syndrome is poorly characterized in dogs. In
but lymphocyte counts of more than 500,000/µL are rare. In our experience, most dogs with extreme neutrophilia have
dogs with CLL, B-cell (i.e., CD21-positive) and T-cell (i.e., leukemoid reactions and not CML. Some of the markers
CD4/CD8-positive) CLLs were almost equally distributed used to diagnose CML in humans are of no use in dogs. For
(Comazzi et al., 2011). In addition to the lymphocytosis, example, the Philadelphia 1 chromosome and the alkaline
which may be diagnostic in itself (e.g., a dog with a phosphatase score were originally used in humans to