Page 1289 - Clinical Small Animal Internal Medicine

133 Lymphoid Leukemias, Myeloid Neoplasia, and Myelodysplastic Syndrome 1227

progression of the malignancy, treatment is often limited
VetBooks.ir to palliative cytoreductive chemotherapy with such
drugs as cytosine arabinoside, doxorubicin, vincristine,
and cyclophosphamide. Intensive supportive care is
commonly necessary and may include blood and/or
platelet‐rich plasma infusion along with aggressive anti­
biotic therapy for infection.

Prognosis
The prognosis for AML is considered poor. In one study
of 16 dogs with confirmed AML, median and mean sur­
vival after diagnosis were 7 days and 20 days respectively
with a range of 2–138 days. Most of the dogs in the study
were treated with chemotherapy. However, protocols
were not consistent and some dogs were euthanized
before any treatment could be instituted due to rapidly
progressive clinical signs. There is one case report of a
dog with megakaryoblastic leukemia that demonstrated
a lengthy survival of 24 months with treatment so all
AML is not necessarily rapidly fatal. For some dogs,
Figure 133.3 Photomicrograph of poorly differentiated blast cells HSCT may be feasible. For those animals, HSCT offers
in the peripheral blood of a dog that has myelomonocytic the possibility of prolonged survival and cure.
leukemia diagnosed via flow cytometry. The neoplastic cells are
large with pleomorphic nucleoli and prominent nucleoli. Wright
Giemsa stain, 1000× magnification. Source: Courtesy of Dr Jan Myeloproliferative Neoplasms
Andrews, Antech Diagnostics.
Myeloproliferative neoplasms (MPNs) are defined as
overproduction of differentiated bone marrow cells which
Table 133.1 lists immunophenotypic markers for
uncharacterized leukemias in animals recommended by results in the accumulation of the affected cell (granulo­
cytes and/or monocytes, erythrocytes or platelets).
the ACVP Oncology Committee.
Chronic Myelogenous Leukemia
Therapy Etiology/Pathophysiology
The course of the disease is short, usually only days to Chronic myelogenous leukemia (CML) in dogs is charac­
weeks, and animals quickly succumb or are euthanized terized by a neoplastic proliferation of the neutrophil
soon after diagnosis. Traditional chemotherapy alone is series and is more similar to human chronic neutrophilic
largely unrewarding due to inadequate or short‐term leukemia than human CML. Human CML is associated
responses. As with other forms of leukemia, HSCT is with the proliferation of several hematopoietic cell line­
becoming a viable treatment option for dogs with leuke­ ages due to the presence of a BCR‐ABL translocation
mia. However, owing to limited availability and rapid
(Philadelphia chromosome) between chromosomes 9
and 22. The regions of human chromosomes 9 and 22 are
Table 133.1 Recommended immunophenotyping markers evolutionarily related to regions on canine chromosomes
to differentiate animal leukemias as proposed by the Myeloid
Neoplasm Subcommittee of the American College of Veterinary 9 and 26 and a canine equivalent to the BCR‐ABL muta­
Pathologists tion (Raleigh chromosome) has been identified in three
cases of canine CML. The etiology of most canine and
Cell type Immunophenotypic marker(s) feline CML is unknown.

B lymphocytes CD79a Signalment
T lymphocytes CD3 There is no known age, sex, or breed predilection in
Myeloid MPO, CD11b canine CML. FeLV infection has been associated with
Megakaryoblastic CD41 CML in cats.
Dendritic cells CD1c
Acute leukemia CD34
History/Clinical Signs
Source: McManus PM. Classification of myeloid neoplasms: a
comparative review. Vet Clin Pathol 2005; 34: 189–212. Reproduced Many patients have no clinical signs until significant
with permission of John Wiley & Sons. organ infiltration or myelophthisis of the bone marrow