Page 718 - Withrow and MacEwen's Small Animal Clinical Oncology, 6th Edition

696 PART IV Specific Malignancies in the Small Animal Patient

Dogs with intravascular lymphoma usually present with signs TABLE 33.2 Differential Diseases or Conditions That
related to CNS, PNS, or ocular involvement, 84–88 including Can Resemble Canine Lymphoma
paraparesis, ataxia, hyperesthesia, seizures, blindness, lethargy,
VetBooks.ir anorexia, weight loss, diarrhea, polyuria, polydipsia, and intermit- Form of Lymphoma Other Disorders
tent fever. Finally, dogs with pure hepatosplenic lymphoma usu-
ally present with nonspecific signs of lethargy, inappetence and Multicentric Disseminated infections: bacterial, viral, rick-
ettsial, parasitic, fungal
weakness, and often are icteric. 81–83 Immune-mediated disorders: dermatopathies,
Canine lymphoma also may be associated with paraneoplastic vasculitis, polyarthritis, lupus erythrema-
syndromes (see Chapter 5). Anemia is the most common lym- tosus
phoma-related paraneoplastic syndrome. 140 Paraneoplastic hyper- Tumors metastatic to nodes
calcemia is also common and is characterized clinically by anorexia, Other hematopoietic tumors: leukemia, multiple
weight loss, muscle weakness, lethargy, polyuria, polydipsia, and, myeloma, malignant or systemic histiocy-
rarely, CNS depression and coma. Lymphoma-induced hypercal- tosis
cemia in most cases results from parathyroid hormone–related pep- Mediastinal Other tumors: thymoma, chemodectoma,
tide (PTHrP), elaborated by neoplastic cells; however, it can also be ultimobranchial cyst, ectopic thyroid carci-
related to the production of several other humoral factors, includ- noma, pleural carcinomatosis, pulmonary
ing interleukin-1 (IL-1), tumor necrosis factor-alpha (TNF-α), lymphomatoid granulomatosis a
transforming growth factor-beta (TGF-β), and vitamin D analogs Infectious disease: granulomatous disease,
pyothorax
(e.g., 1,25-dihydroxyvitamin D). 114,115,141–143 As previously dis- Miscellaneous: congestive heart failure, chylo-
cussed, hypercalcemia is most commonly associated with the T-cell thorax, hemothorax
immunophenotype. Other paraneoplastic syndromes that may be
encountered include monoclonal gammopathies, neuropathies, and Alimentary Other gastrointestinal tumors, foreign body,
cancer cachexia. lymphangiectasia, lymphocytic-plasmacytic
enteritis, systemic mycosis, gastroduodenal
ulceration
Diagnostics Cutaneous Infectious dermatitis: advanced pyoderma
For dogs with suspected lymphoma, the diagnostic evaluation Immune-mediated dermatitis: pemphigus
should include a thorough physical examination; complete blood Other cutaneous neoplasms (in particular
count (CBC), including differential leukocyte and platelet counts; histiocytic disorders)
a serum biochemical profile; and urinalysis. Optimally, plasma Extranodal Variable, depending on organ/system involved
ionized calcium concentration should be measured. Ultimately,
obtaining tissue or cytologic specimens (or both) for a definitive a The existence of this disease is controversial; in most cases the disease has been reclassi-
diagnosis is essential. The differential diagnosis of lymphadenopa- fied as a lymphoid neoplasm.
thy depends on the travel history of the dog (i.e., relative to infec-
tious disease) and the size, consistency, and location of affected
LNs. Other causes of lymphadenopathy include infections caused
by bacteria, viruses, protozoa (Toxoplasma sp., Leishmania sp.), funduscopic assessment, may reveal abnormalities (e.g., uveitis,
rickettsial organisms (salmon poisoning, Ehrlichia sp.), and fun- retinal hemorrhage, ocular infiltration, glaucoma) in approxi-
gal agents (Blastomyces and Histoplasma sp.). The potential for mately one-third to one-half of dogs with lymphoma. 139,144
hypercalcemia to accompany systemic fungal diseases may further
complicate differentiation from lymphoma. Discrete, hard, asym- Complete Blood Count, Biochemical Profile,
metric LNs, particularly if they are fixed to underlying tissues, and Urinalysis
may indicate metastatic tumors such as mast cell tumor or car- Anemia, the most common lymphoma-related hematologic
cinoma. Immune-mediated diseases (e.g., pemphigus, systemic abnormality, is usually normochromic and normocytic (non-
lupus erythematosus, and immune-mediated polyarthropathy) regenerative), consistent with anemia of chronic disease 140 ; how-
also may result in mildly to moderately enlarged LNs. The various ever, hemorrhagic and hemolytic anemias may also occur, and
differential diseases or conditions that can resemble canine lym- regenerative anemias may reflect concomitant blood loss or hemo-
phoma are listed in Table 33.2. lysis. In addition, if significant myelophthisis is present, anemia
may be accompanied by thrombocytopenia and leukopenia. 145,146
Physical Examination In animals with anemia or evidence of bleeding, in addition to a
A thorough physical examination should include palpation of all platelet count, a reticulocyte count and coagulation testing may
assessable LNs and rectal examination, as in the authors’ expe- be indicated. Thrombocytopenia occurs in 30% to 50% of cases,
rience, a significant proportion of dogs will have rectal polyps but bleeding is seldom a clinical problem. Neutrophilia occurs in
consisting of aggregates of neoplastic lymphocytes. Inspection 25% to 40% of dogs and lymphocytosis occurs in approximately
of mucous membranes for pallor, icterus, petechiae, and ulcer- 20% of affected dogs. Circulating atypical lymphocytes may be
ation should be undertaken as these signs may indicate anemia indicative of bone marrow involvement and leukemia. It is impor-
or thrombocytopenia secondary to myelophthisis or immune- tant to differentiate multicentric lymphoma with bone marrow
mediated disease or may be evidence of major organ failure or involvement (i.e., stage V disease) from primary lymphocytic leu-
uremia. Abdominal palpation may reveal organomegaly, intestinal kemia because the prognosis for each may be different. Hypopro-
wall thickening (if marked), or mesenteric lymphadenopathy. The teinemia is observed more frequently in animals with alimentary
presence of a mediastinal mass and/or pleural effusion can be sus- lymphoma. In dogs with a high total protein concentration or evi-
pected after thoracic auscultation. Ocular examination, including dence of an increased globulin fraction on a biochemical profile,