Page 1328 - Small Animal Internal Medicine, 6th Edition

1300 PART XII Oncology

TABLE 79.3
VetBooks.ir TNM Staging System for Dogs and Cats With Lymphoma

STAGE
CLINICAL FEATURES
I Solitary lymph node involvement
II More than one lymph node enlarged but on
one side of the diaphragm (i.e., cranial or
caudal)
III Generalized lymph node involvement
IV Stage III findings, plus hepatomegaly and/or
splenomegaly
V Any of the above, plus bone marrow or
extranodal involvement
Substage a: asymptomatic
FIG 79.9 Substage b: sick
Cytologic features of large cell lymphoma in a dog. Large,
neoplastic lymphoid cells (red arrow), intermixed with TNM, Tumor, node, metastasis.
normal small lymphocytes (blue arrow). Note
lymphoglandular bodies (yellow arrow), islands of
cytoplasms from broken neoplastic cells.

flow cytometric, or molecular evaluation of a lymph node or major benefits: (1) It is associated with minimal or no mor-
mass to establish a diagnosis. bidity, and (2) it is financially acceptable to most owners (i.e.,
Pathologists have advocated the use of an adaptation of approximate cost of a lymph node aspirate is $200-$300; the
the human World Health Organization’s histopathologic cost for biopsy and histopathologic evaluation is $500-$700).
classification of non-Hodgkin lymphomas for several New diagnostic methodologies commonly used in
decades. Recently, Valli et al. (2013) proposed a modified patients with lymphoma in our clinics include immunophe-
system that may have prognostic implications. However, it notyping by FCM and clonal analysis by polymerase chain
includes more than 30 different categories of tumors, usually reaction (PCR). In the former, a sample of the affected organ/
requires histopathologic evaluation of an entire lymph node, tissue is obtained by FNA and placed in appropriate trans-
and specific diagnoses may not be consistent among pathol- port media. In the laboratory, these cells are incubated with
ogists. In this scheme, the authors (and others) recognized a specific antibodies that recognize epitopes specific for T or
subset of multicentric indolent lymphomas, in which sur- B cells. FCM evaluation of the sample allows to immunophe-
vival times with minimal treatment (see later) are common. notype the cell population as T or B cell derived. Immuno-
These subtypes include mainly mantle zone lymphoma phenotyping by FCM is now performed by some diagnostic
(MZL-intermediate cell, B-cell) and T zone lymphoma reference laboratories. Immunophenotyping can also be
(TZL-small cell, T-cell) (Deravi et al., 2017; Flood-Knapik carried out on lymph node or tissue biopsies immunohisto-
et al., 2013; Valli et al., 2013). Most dogs with TZL are chemically or previously submitted cytology slides by immu-
Golden Retrievers, Shih Tzus, and Labrador Retrievers. The nocytochemistry. Clonal analysis by PCR (or PCR for antigen
combination of cytologic appearance and FCM allows for receptor rearrangement [PARR]) also requires an FNA or a
classification of these tumors as indolent (Deravi et al., 2017; small biopsy specimen. Specific laboratories will evaluate the
Flood-Knapik et al., 2013). There is also a specific splenic population of cells in question by PCR to determine if they
indolent lymphoma in dogs, termed marginal zone lym- are monoclonal or polyclonal. This technique has high sen-
phoma; this tumor usually presents as a solitary splenic mass sitivity and specificity for distinguishing reactive lymph-
(as opposed to diffuse splenomegaly) and can be effectively adenopathy from lymphoma in dogs and cats. As a general
treated with splenectomy alone, resulting in prolonged sur- rule, the authors use FCM to immunophenotype lymphomas
vival times (O’Brien et al., 2013). and PARR when the diagnosis of lymphoma is in question
Until there is conclusive evidence that the histopatho- (i.e., to confirm or rule out lymphoma).
logic classification of canine and feline lymphomas offers After a diagnosis of lymphoma is confirmed, it is custom-
conclusive prognostic or therapeutic information, the surgi- ary to stage the disease to obtain a prognosis. A staging
cal removal of a lymph node or extranodal mass for histo- system devised by the World Health Organization has been
pathologic evaluation in a patient with a cytologic diagnosis used routinely for the staging of cats and dogs with lym-
of lymphoma is not generally indicated. A diagnosis based phoma (Table 79.3). In this system, derived from the tumor,
on cytologic findings rather than histopathologic findings node, metastasis (TNM) staging system for neoplasms in
yielded by an excisional lymph node biopsy also offers two humans, clinical and clinicopathologic information from the