Feline lymphoma 1. Principles of diagnosis and management
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Feline lymphoma 1. Principles of diagnosis and management


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In Practice \ufffd O C T O B E R 20 06516
PRESENTATION
There are three well-recognised forms of feline lymph-
oma \u2013 mediastinal, alimentary and multicentric \u2013 and 
the clinical presentation of each reflects the areas of 
involvement. In addition, the disease can arise wherever 
there is lymphoid tissue and this anatomical subdivision 
can be difficult to define and may even be misleading 
when attempting to compare treatment response between 
small subgroups of cats. Importantly, there is also a 
large and disparate group of other sites that can be com-
monly affected. The site of involvement can be related to 
age and feline leukaemia virus (FeLV) status (see table 
below). Unlike dogs, cats infrequently present with gen-
eralised lymphadenopathy and rarely present with para-
neoplastic hypercalcaemia. 
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LYMPHOMA is the most common malignancy in cats and accounts for approximately one-third of all 
feline tumours. Feline lymphoma in its various guises is a relatively frequent diagnosis in UK practice. 
This range of presentations poses a diagnostic challenge for practitioners, and persistence and 
resourcefulness are often needed to obtain a definitive diagnosis. Furthermore, response to treatment 
is not always easy to predict as many cats enjoy sustained remission and even cure with practice-based 
therapy, while other cases respond poorly and thus have a limited life expectancy. Communicating 
the evidence to an owner while presenting a fair and realistic overview of what is to be expected can 
be difficult, but this is necessary to achieve informed consent and owner involvement in therapeutic 
decision-making. This article discusses diagnostic and management principles for feline lymphoma, and 
reviews the current literature on therapy as it pertains to choices in case management in the practice 
setting. Part 2, to be published in the next issue, will focus on specific disease presentations.
Feline lymphoma
1. Principles of diagnosis 
and management ALISON HAYES
In Practice (2006) 
28, 516-524
DIAGNOSIS
In many cases, a compilation of history, signalment, and 
clinical, viral and cytological information can establish 
a working diagnosis. For certain sites (eg, kidney, liver 
and abdominal nodes), cytology can provide a relatively 
non-invasive, inexpensive and rapid diagnosis. However, 
wherever possible, this should be reinforced by histo-
pathology, especially where cytology yields a population 
of small lymphocytes or if findings are inconclusive. 
A Tru-cut style core biopsy device can be safely used 
to obtain tissue for histopathology from larger lym-
phoid masses and mediastinal, renal or gastrointestinal 
Alison Hayes 
graduated from 
Glasgow in 1991 
and spent five years 
in mixed and small 
animal practice in 
north-west England. 
She subsequently 
undertook a 
three-year Blue 
Cross residency in 
oncology at the 
Animal Health Trust 
in Newmarket, 
where she is now a 
clinical oncologist. 
She holds the 
RCVS certificate in 
veterinary radiology 
and an MSc 
in clinical oncology 
from the University 
of Birmingham 
medical school.
PRESENTATIONS OF FELINE LYMPHOMA RELATED TO AGE AND FeLV STATUS
Presentation Age T cell association FeLV status
Relative frequency 
of occurrence
Mediastinal/
thymic
Young High Majority positive 10-20%
Alimentary Older High Minority positive 50-70%
Multicentric Variable Variable Variable 60-70%
Renal Variable Variable Variable 5-10%
Nasal Older Low Minority positive 10%
Others Variable Variable Variable 5-25%
Incidence and aetiology
It is estimated that the incidence of feline lympho-
ma is approximately 200 cases per 100,000 cats, 
which is higher than in other species. The true inci-
dence is difficult to measure, as prevalence and 
anatomical presentation of the disease vary with 
geographical location, but it appears to be reduc-
ing. The variation in incidence has been attrib-
uted to a number of possible factors, although 
differences in FeLV status of the cat population 
are believed to be primarily responsible. For cases 
without viral association, the exact aetiology of 
the disease is unknown. 
This Siamese cat presented as a 10-month-old 
kitten with a prescapular mass measuring 5 x 
3·5 cm. Further investigation revealed a large 
mediastinal mass extending through the 
cervical inlet to the prescapular region, which 
was confluent with the mass found on clinical 
examination. Lymphoma was diagnosed 
following incisional biopsy of the prescapular 
mass. The cat remains well and disease-free 
three years after completing a course of 
combination chemotherapy
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In Practice \ufffd O C T O B E R 20 06 519
lesions under ultrasound guidance. Where a peripheral 
lymphadenopathy is present or lymph node sampling is 
required for staging, an excisional biopsy of the node 
is ideal. Nasal biopsy can be difficult and unreward-
ing in the cat; sometimes several attempts are needed 
before a definitive diagnosis is achieved. In the author\u2019s 
experience, forced nasal flushing is often unsatisfac-
tory and contraindicated if the integrity of the cribri-
form plate is compromised. Aspiration techniques using 
a 14 gauge intravenous catheter or 10 French gauge dog 
urinary catheter can be used to obtain a suction biopsy 
via the nostril. The catheter should be premeasured to 
the medial canthus to avoid inadvertent sampling through 
the cribriform plate. Biopsy material should be expelled 
onto a clean swab to absorb blood and secretions, and 
the remainder used to make impression smears or sub-
mitted in formalin for histology. A blind grab biopsy 
technique can also be used, as can retrograde endoscopy 
to visualise and sample lesions. Computed tomography 
and magnetic resonance imaging can assist with identi-
fication of a bony window through which material for 
cytology can be obtained. 
Although immunohistochemistry can be useful in 
aiding definitive diagnosis, especially in cases of gastro-
intestinal lymphoma, it does not appear to offer prognos-
tic information in cats. 
All samples for diagnostic purposes should be taken 
prior to administering chemotherapeutic drugs, including 
glucocorticoids.
CLASSIFICATION AND STAGING
The classification of lymphoma in cats is based on ana-
tomical site and cell morphology. Staging is achieved by 
applying the World Health Organization (WHO) system 
(see table, below left), which sets out various criteria 
and is useful for reporting findings to colleagues, docu-
menting disease progression, and effectively defining 
a study population. The system has been further adapt-
ed for feline lymphoma (Mooney and others 1989) but, 
despite this, remains a generally unsatisfactory way of 
defining the disease in cats. Of 
more importance in the clini-
cal management of a case is 
docu mentation of all areas 
of involvement so that the 
response to treatment can