Page 747 - Withrow and MacEwen's Small Animal Clinical Oncology, 6th Edition

CHAPTER 33 Hematopoietic Tumors 725

study. 506 In a series of cats with various anatomic forms of lym- • BOX 33.5 Clinical Staging System for Feline

phoma, serum albumin concentrations were significantly lower Lymphoma 558
and β-globulin concentrations (as measured by protein elec-
VetBooks.ir trophoresis) were significantly higher than a healthy control Stage 1
population.
507
• A single tumor (extranodal) or single anatomic area (nodal)
The use of various imaging modalities in cats with lymphoma • Includes primary intrathoracic tumors
depends on the anatomic site and will be discussed in site-specific
discussions to follow. Stage 2
Cytopathologic or histopathologic evaluation of involved • A single tumor (extranodal) with regional lymph node involvement
lymph node(s) or involved organ tissue, procured via FNA cytol- • Two or more nodal areas on the same side of the diaphragm
ogy (see Chapter 7) or surgical, endoscopic, or needle-core biopsy • Two single (extranodal) tumors with or without regional lymph node
involvement on the same side of the diaphragm
(see Chapter 9), is required for a definitive diagnosis. Cytology • A resectable primary gastrointestinal tract tumor, usually in the ileocecal
alone may not be sufficient in some cases, owing to difficulties area, with or without involvement of associated mesenteric nodes only
encountered in distinguishing lymphoma from benign hyper-
plastic or reactive lymphoid conditions. In such cases, incisional Stage 3
or excisional biopsy is preferred as orientation and information • Two single tumors (extranodal) on opposite sides of the diaphragm
regarding invasiveness and architectural abnormalities may be • Two or more nodal areas above and below the diaphragm
necessary for diagnosis. In addition, involved tissue, needle aspi- • All extensive primary unresectable intraabdominal disease
rate, and fluid samples can be further interrogated by various • All paraspinal or epidural tumors, regardless of other tumor site or sites
histochemical, immunohistochemical, flow cytometric analysis Stage 4
(e.g., size and immunophenotypic assessment), and molecular
techniques (e.g., PARR to assess clonality) to further character- • Stages 1–3 with liver and/or spleen involvement
ize the disease process and refine the diagnosis in equivocal cases. Stage 5
The reader is referred to Chapter 8 for a general discussion of flow • Stages 1–4 with initial involvement of CNS or bone marrow or both
cytometric analysis and molecular diagnostic techniques, as well
as Section A of this chapter for specific applications to lymphoma.
PARR in cats is approximately 80% sensitive for the diagnosis
of lymphoma 553 ; however, assessment of specificity has not been This provides only general observations rather than specific out-
clearly established. Clonality assessment tools (e.g., primers) for come information (i.e., response rate and durability of response)
both Ig and T-cell receptor variable region genes have been devel- that can vary significantly with respect to anatomic and histologic
oped in cats. 479,480,554–557 subtype. Most treatment decisions should be based on assessment
Assessment of tumor proliferation rates (e.g., Ki67, PCNA, of whether the individual case represents a low-grade (e.g., indo-
AgNOR), telomerase activity, and serum protein electrophore- lent) versus an intermediate- or high-grade (e.g., large cell) lym-
sis can also be performed on involved tissues in cats; however, phoma and whether the disease is limited to the local extranodal
consistent prognostic value across the anatomic, histopathologic, site. Chemotherapy protocols for the cat have been previously
and immunophenotypic variants of lymphoma in cats is not well discussed under sections in GI lymphoma; low-grade tumors are
characterized. generally treated with chlorambucil/prednisolone protocols and
Thorough staging, including a bone marrow aspiration or intermediate- or high-grade tumors with CHOP- or COP-based
biopsy, peripheral lymph node assessment (clinically normal or protocols. Finally, much of the early work on chemotherapy pro-
abnormal nodes), and thoracic and/or abdominal imaging, is indi- tocol development for cats with lymphoma occurred during the
cated when (1) solitary site disease is suspected (stage I) and a FeLV era and care should be exercised when applying this infor-
decision between locoregional therapy (i.e., surgery and/or RT) mation in the post-FeLV era.
versus systemic therapy (i.e., chemotherapy) is being considered;
(2) it provides prognostic information that will help a caregiver Nasal Lymphoma
make treatment decisions; and (3) complete staging of the extent
of disease is required as part of a clinical trial. Bone marrow evalu- Nasal lymphoma is the most common extranodal lymphoma in
ation may be of particular interest if anemia, cellular atypia, and/ cats. 559 It is usually a localized disease; however, 20% have local
or leukopenia are present. A WHO staging system exists for the extension or distant metastasis at necropsy. 560 The majority of non-
cat that is similar to that used in the dog (see Box 33.2); however, viral nasal/paranasal diseases in cats are neoplasia, and lymphoma
because of the high incidence of visceral/extranodal involvement represents one-third to one-half of these cases. 561–564 It occurs
in cats, a separate staging system has been evaluated and is often primarily in older (median age, 9–10 years; range, 3–17 years),
used (Box 33.5). 558 Because lymphoma in cats is more varied with FeLV/FIV antigenemic negative cats, and at least three-quarters
respect to anatomic locations, staging systems are generally less are B-cell in origin, although T-cell and mixed B-cell/T-cell immu-
helpful for predicting response. nophenotypes are reported in 10% to 15% of cases. 428,559–561,565
Our knowledge base for treating cats with extranodal lym- An Italian report documented FeLV antigen (p27 or gp70) expres-
phoma is not well established, and outcomes are less predictable sion in nasal lymphoma tissues by immunohistochemistry (IHC);
than that in dogs, primarily due to the greater variation in his- however, FeLV antigenemia was not reported in this cohort. 561
tologic type and anatomic location observed in cats. This is fur- Siamese cats appear overrepresented and a 2:1 male-to-female
ther complicated by the plethora of papers that include very small ratio has also been observed. 561,565 Most are of intermediate- or
numbers of cases representing multiple anatomic/immunopheno- high-grade histology; however, small-cell low-grade variants have
typic and histologic subtypes (e.g., small cell vs large cell variants) been reported in up to 25% of some cohorts. 560,561,565 Epitheliot-
together when reporting survival analysis after chemotherapy. ropism is common if the epithelium is present in the biopsy.