Page 739 - Withrow and MacEwen's Small Animal Clinical Oncology, 6th Edition

CHAPTER 33 Hematopoietic Tumors 717

TABLE 33.9 General Characteristics of the Most Commonly Encountered Anatomic Forms of Lymphoma in Cats
Immuno- Local versus
VetBooks.ir Anatomic Relative Median Age Phenotype FeLV Antigenicity Diffuse/ Biologic General
(yr)
Form
Frequency
(Generally)
Prognosis
Behavior
Multicentric
Alimentary/
Gastroin-
testinal
LGAL Common 10–13 T-cell, small Rare Diffuse Indolent Good
I/HGAL Uncommon 12 B-cell, large Rare Generally Diffuse Aggressive Poor–Fair
LGL Uncommon 9 T-cell, large Rare Generally Diffuse Aggressive Poor
Nasal Uncommon 9–10 B cell (75%) Rare Local common More indolent Good–Fair
Mediastinal Uncommon 2–4 T-cell, large More common Local common Indolent or Fair–Poor
aggressive
forms
Peripheral
nodal
Non-Hodg- Uncommon 3–4 B-cell (75%), More common Multicentric Aggressive Fair–Poor
kin’s large
Hodgkin’s- Rare 11 T-cell rich B-cell, Rare Local initially Indolent Good– Fair
like large
Laryngeal/ Rare 9 ID Rare Local common ID Fair–Good
Tracheal
Renal Uncommon 9 B-cell Rare Multicentric Aggressive Poor–Fair
CNS Rare 4–10 ID Rare Multicentric Aggressive Poor
Cutaneous Rare 10–13 T-cell Rare Local initially Indolent to Fair
aggressive
Subcutane- Rare 10–13 B-cell, large Rare Local initially Aggressive Fair
ous
Ocular Rare 10–11 B-cell Rare Local Often indolent Good–Fair
(PSOL)

Common = >50% of clinical presentations; Moderate = 20%–50% of clinical presentations;
Uncommon = 5%–20% of clinical presentation; Rare = <5% of clinical presentations.
ID, Insufficient data; I/HGAL, intermediate-/high-grade alimentary lymphoma; LGAL, low-grade alimentary lymphoma; LGL, = large granular lymphoma; PSOL, presumed solitary ocular lymphoma.

FIV antigenemia was only rarely associated with alimentary lym- (see Chapter 2) has been documented in feline lymphoma tis-
phoma in other large compilations of cases. 428,458–461 sues. 464,465 Alterations in cellular proliferation and in cell-cycle
Interrogations of gammaherpesvirus 1(FcGHV1) in cats with and death (apoptosis) pathways, in particular the cyclin-dependent
lymphoma did not show an association; however, FcGHV1 anti- kinase cell-cycle regulators and the Bcl-2 family of proapoptotic
genemia was associated with an overall poorer prognosis for cats and antiapoptotic governing molecules, have also been implicated
with lymphoma, the causality of which is speculative. 462 in feline lymphoma. 466–468
Genetic and Molecular Factors Environmental Factors
As discussed in Section A of this chapter (canine lymphoma), Evidence for exposure to environmental tobacco smoke (ETS) as a
recent advances in molecular cytogenetics (see also Chapter 1, risk factor for lymphoma in humans has prompted investigations in
Section A, and Chapter 8), including gene microarray techniques, cats. In one report, the relative risk of developing lymphoma in cats
have and are currently being applied to investigations of chromo- with any exposure to ETS and with 5 or more years of exposure to
somal aberrations and gene expression changes in veterinary spe- ETS was 2.4 and 3.2, respectively. 469 A large European study docu-
cies with lymphoma. Indeed, a predisposition of the oriental cat menting an association between proximity of waste management
breeds to develop lymphoma suggests a genetic predisposition and and cancer in dogs failed to show increased risk in cats. 470
indicates heritable risk. 427,435,436 Altered oncogene/tumor sup-
pressor gene expression, epigenetic changes, signal transduction, Immunosuppression
and cell death-pathway alterations are common in lymphomas Immune system alterations in the cat, such as those accompany-
of humans and are likely also involved in the cat. Several genetic ing FIV infection, has been implicated in the development of lym-
factors have already been discussed as they relate to FeLV asso- phoma. 450,452,454,471 As is the case in immunosuppressed human
ciations. In addition, N-ras aberrations have been implicated, organ transplantation patients, reports of immunosuppressed feline
although they are rare in cats. 463 Furthermore, telomerase activity renal transplant recipients document increased risk of lymphoma