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588 Leukemias, Chronic

molecular abnormalities that cause them • For severely neutropenic patients, wear • Instruct owners to avoid exposure to
may improve the prognosis in the future. gloves when handling, and avoid exposure chemotherapy.
VetBooks.ir Technician Tips • For severely thrombocytopenic patients, SUGGESTED READING
to patients with infections.
take precautions to avoid hemorrhage with
• Patients with AL are often sick and pan-
Young KM, et al: Hematopoietic tumors. In Withrow
cytopenic. With response to treatment,
venipuncture.
clinical signs may worsen before improving. • Instruct owners to monitor for lethargy, loss SJ, et al, editors: Small animal clinical oncology,
ed 5, St. Louis, 2013, pp 608-678.
Hospitalization for supportive care and of appetite, vomiting, diarrhea, bleeding, and AUTHOR: Nicole C. Northrup, DVM, DACVIM
monitoring is required. signs of anemia and to call if noted. EDITOR: Kenneth M. Rassnick, DVM, DACVIM

Leukemias, Chronic Client Education
Sheet

Clinical Presentation
BASIC INFORMATION • Progression is insidious. Bone marrow
DISEASE FORMS/SUBTYPES infiltration results in myelophthisis (crowd-
Definition CLL (dogs): ing of normal cells, changes in the marrow
• Chronic leukemias (CLs) are clonal prolifera- • T-cell phenotype more common, large microenvironment, and secretion of suppres-
tions of malignant mature hematopoietic cells granular lymphocyte (LGL) common sor factors) or myelofibrosis and consequent
in the bone marrow. • Atypical phenotypes: ≈15% anemia, neutropenia, thrombocytopenia.
• Chronic lymphocytic leukemia (CLL) is CLL (cats): • Hepatic and splenic infiltration results in
an indolent proliferation of mature lym- • T-cell phenotype more common organomegaly, abdominal distention, and loss
phocytes, similar to low-grade lymphocytic MPN: of appetite. Organ dysfunction is possible.
lymphoma. • CML • Transformation may lead to blast crisis.
• Myeloproliferative neoplasms (MPNs), also • Chronic neutrophilic leukemia (CNL)
called chronic myeloid leukemias (CMLs), • Chronic monocytic leukemia (CMoL) DIAGNOSIS
are proliferations of mature granulocytes • Chronic myelomonocytic leukemia (CMML
and/or monocytes, erythrocytes, platelets or CMMoL) Diagnostic Overview
or of eosinophils, basophils, or mast • Chronic eosinophilic leukemia (CEL) CL is diagnosed based on a high count of a
cells. • Chronic basophilic leukemia (CBL) cell line on CBC and/or bone marrow cytology
• Mast cell leukemia (MCL) or histopathology. CLL immunophenotype is
Epidemiology • Primary erythrocytosis (PV) determined with flow cytometry of blood or
SPECIES, AGE, SEX • Primary thrombocytosis (i.e., essential bone marrow. Distinction between CLL and
• CLL is uncommon in dogs and rare in cats; thrombocythemia [ET]) low-grade lymphocytic lymphoma is not always
MPN is rare. possible.
• Middle-aged to older dogs and cats HISTORY, CHIEF COMPLAINT
• Incidental increased peripheral blood count Differential Diagnosis
GENETICS, BREED PREDISPOSITION of affected cell line • Based on type of cell(s) involved
• Primary erythrocytosis (i.e., polycythemia • Lethargy, loss of appetite, weight loss, and • Lymphocytes: CLL, low-grade lymphocytic
vera [PV]): JAK2 mutations (dogs) signs due to cytopenias (weakness, hemor- or LGL lymphoma, ehrlichiosis, viral
• Chronic myeloid leukemia (CML): BCR-ABL rhage, infection) infection (FeLV, feline herpesvirus type
fusion gene (i.e., Raleigh chromosome) • PV (rarely CLL): seizures, syncope, behavior 1), chronic antigenic stimulation (e.g.,
• B-cell CLL: small breeds; Bichon frisé, changes, blindness, ataxia (due to hypervis- inflammatory bowel disease, cholangiohepa-
Boston terrier, Cairn terrier, cocker spaniel, cosity), polyuria/polydipsia titis), vaccination, stress/epinephrine (cats,
dachshund, English bulldog, Jack Russell • CEL (cats): GI signs due to infiltration typically < 20,000 cells/mcL), pure red cell
terrier, Maltese, pit bull, Pomeranian, shih • Some MPN signs are due to cytokines or aplasia, immune-mediated hemolytic anemia,
tzu, and Yorkshire terrier other factors (e.g., CBL, MCL: GI signs due hypoadrenocorticism, feline hyperthyroidism,
to histamine). thymoma
RISK FACTORS • Neutrophils: CML/CNL or extreme neu-
CLL is not associated with feline leukemia PHYSICAL EXAM FINDINGS trophilia due to infection (e.g., pyometra,
virus (FeLV) or feline immunodeficiency virus • Initially normal hepatozoonosis), tissue necrosis, autoimmune
(FIV). • Hepatomegaly/splenomegaly as disease disease (e.g., immune-mediated hemolytic
progresses anemia), hemorrhage, drug reaction,
ASSOCIATED DISORDERS • CLL (dogs): lymphadenomegaly congenital disorders (e.g., leukocyte adhe-
• CLL: monoclonal gammopathy (English bull- • PV: brick red mucous membranes, neurologic sion deficiency), or paraneoplastic syndromes
dogs predisposed), hyperviscosity syndrome, signs, retinal hemorrhages, tortuous retinal associated with nonhematologic or lymphoid
hypercalcemia, anemia vessels cancers
• PV: hyperviscosity syndrome • CEL (cats) and MCL: palpable GI thickening • Monocytes: CMoL, CMML, chronic infection/
• CML: myelofibrosis inflammation, granulomatous disease
• Chronic basophilic leukemia (CBL) and MCL: Etiology and Pathophysiology • Eosinophils: CEL, hypereosinophilic syn-
hyperhistaminemia, urticaria, gastrointestinal • CLs arise from uncontrolled proliferation of drome, parasites, eosinophilic granuloma
(GI) signs/ulceration hematopoietic cells in bone marrow or spleen. complex, mast cell neoplasia, feline asthma,

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