Page 720 - Withrow and MacEwen's Small Animal Clinical Oncology, 6th Edition

698 PART IV Specific Malignancies in the Small Animal Patient

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A B

C D

• Fig. 33.7 Lymph nodes from dogs with lymphoma. (A) Fine-needle aspirate. Note the homogeneous
population of large lymphoid cells with prominent nucleoli and basophilic cytoplasm. These cells are larger
than the neutrophil (black arrow) in the field. Mitotic figures (thin white arrows) and tingible-body mac-
rophages (thick white arrows) also are present. (Wright’s stain, ×60 objective.) (B) Fine-needle aspirate
stained for immunoreactivity for CD79a. Note that nearly all of the lymphocytes express CD79a. The diag-
nosis was B-cell lymphoma. (Alkaline phosphatase/Fast Red, ×60 objective.) (C) Histologic section. Note
effacement of normal architecture. The white spaces are macrophages, giving a “starry sky” appearance
to the lymph node. (H&E, ×20 objective.) (D) Histologic section. Note the presence of tumor cells outside
the capsule of the lymph node. (H&E, ×20 objective.)

immunophenotypic and clonality assessments of cutaneous biop- antigen expression, argyrophilic nucleolar organizer regions
sies can aid in differentiating lymphoma from benign lymphocytic [AgNOR]), 68,74,101,154,171–177 and clonality (PCR for antigen
lesions. 71,75,77,163 PARR) 81,160,178–187 of the tumor can be determined. Genetic
characterizations of canine lymphoma samples have been inves-
Molecular Diagnostic Techniques tigated and are showing potential for both diagnostic and prog-
Molecular techniques can be used to establish a diagnosis of lym- nostic utility, but are not widely applied and clinical correlates
phoma, but are best used to further characterize the tumor after are currently preliminary. 21,22,24,178,179,188,189 The availability of
the initial diagnosis is made. Indeed, in people, genetic charac- molecular and genetic analyses is increasing in veterinary oncol-
terization of NHL are often used in diagnosis and subtyping. ogy; however, at present, only immunophenotype and PARR
96
Tissues and cells from peripheral blood, LNs, nonlymphoid sites, clonality assays are routinely used in dogs to inform clinical deci-
and effusions can be analyzed by various molecular and cyto- sion making.
genetic means to aid in categorization of subtypes and in cases
that represent a more difficult diagnostic challenge, particularly Immunophenotyping
in cases where reactive lymphocytosis and lymphoma are both Immunophenotyping is used to determine the type of cells
possible based on standard histologic or cytologic assessment. that comprise the tumor, but this technique also can be help-
These include histochemical and cytochemical, immunohisto- ful for making the initial diagnosis and predicting out-
chemical (IHC) and immunocytochemical, flow cytometric, come. 96,164,166–171,190,191 When a heterogeneous population of
polymerase chain reaction (PCR), and cytogenetic techniques. lymphocytes is expected in a tissue, documentation of a homo-
For example, the immunophenotype (B vs T cell), 118,164–171 pro- geneous population of the same immunophenotype is supportive
liferation rate (e.g., expression of Ki67, proliferating cell nuclear of a neoplastic process. The immunophenotype of a lymphocyte