A l i m e n t a r y Lym p h o m a

in Cats and Dogs

Tracy Gieger, DVM

KEYWORDS
 Lymphoma  Lymphosarcoma  Chemotherapy  Cancer
 Lymphoid neoplasia  Gastrointestinal neoplasia

FELINE ALIMENTARY LYMPHOMA

Lymphoma is the most common feline malignancy, and the gastrointestinal (GI) tract is
the most common location for this disease.1 Alimentary lymphoma may affect the
upper or lower GI tract, liver, or pancreas, and is characterized by infiltration with
neoplastic lymphocytes with or without mesenteric lymph node involvement.
Lymphoma can be divided histopathologically into small cell (lymphocytic [LL]; low
grade; well differentiated) or large cell (lymphoblastic [LBL]; high grade) types. At
one institution, feline GI lymphoma was equally divided among those types,2 but in
another study LL occurred 3 times more often than LBL.3 Large granular lymphoma
(LGL) is a subtype that is characterized by the presence of natural killer T lymphocytes
that have characteristic intracytoplasmic granules.4,5 Clinically these types of
lymphoma are distinct entities with different clinical presentations, therapies, and
outcomes.

Etiology and Pathogenesis

Although infection with feline leukemia virus (FeLV) and feline immunodeficiency virus
(FIV) are major risk factors for the development of lymphoma, cats with GI lymphoma
are usually negative for both viruses.1,2 Helicobacter infection may play a role in the
development of feline GI lymphoma.6 In one study, gastric biopsy samples from 16
of 24 cats with lymphoma were positive for Helicobacter heilmannii. The potential
importance of this infection is that eradication of the bacteria with antibiotics may
resolve or hinder the progression of the underlying neoplasm. Exposure to cigarette
smoke is another risk factor for development of lymphoma in cats. Cats living in
households with any exposure to cigarette smoke have a 2.4-fold increased risk of
developing lymphoma than cats from nonsmoking households, and the amount and
duration of exposure is linearly correlated with increasing risk of lymphoma
development.7

Department of Veterinary Clinical Sciences, Louisiana State University School of Veterinary

Medicine, Skip Bertman Drive, Baton Rouge, LA 70803, USA
E-mail address: tgieger@vetmed.lsu.edu

Vet Clin Small Anim 41 (2011) 419–432

doi:10.1016/j.cvsm.2011.02.001 vetsmall.theclinics.com
0195-5616/11/$ – see front matter Ó 2011 Elsevier Inc. All rights reserved.
420 Gieger

Signalment, History, and Physical Examination

Alimentary lymphoma has been reported in cats ranging in age from 1 to 20 years
(median 13 years), with most cats being middle-aged to older.1
Lymphocytic lymphoma is typically a slowly progressive disease with a protracted
history (Table 1). In one study, the median duration of clinical signs of illness before
diagnosis was 6 months.8 Clinical signs included weight loss, vomiting, diarrhea,
anorexia or hyporexia, and lethargy.2 Physical examination findings in cats with LL
may be unremarkable or can reveal diffusely thickened intestinal loops, a mass lesion
consisting of mesenteric lymph nodes, and/or an intramural intestinal mass.2
Lymphoblastic lymphoma is most often characterized by an acute onset of weight
loss, vomiting, diarrhea, anorexia or hyporexia, and icterus if concurrent liver involve-
ment is present (see Table 1). The physical examination often reveals dehydration,

Table 1
Lymphocytic versus lymphoblastic lymphoma

Clinical signs of illness Gradual weight loss, vomiting, Rapid weight loss, anorexia,
diarrhea, decreased appetite vomiting, diarrhea, icterus
Duration of clinical signs Typically prolonged (weeks to Typically acute (days to weeks)
months)
Physical examination May be normal; thickened Palpable mass lesions common;
findings bowel loops; palpable hepatomegaly; icterus
masses uncommon
Diagnostic workup Rule out non-GI causes of Aspiration cytology of mass
weight loss; endoscopy lesions, mesenteric lymph
versus full-thickness surgical nodes or abnormal liver
biopsy required for usually diagnostic
definitive diagnosis
Pitfalls of diagnostic False negatives common when Hepatic lipidosis and
testing and therapy enlarged mesenteric lymph pancreatitis may be
nodes are aspirated; concurrent diseases
histopathology to
differentiate from
inflammatory bowel disease
can be challenging
Surgical intervention Useful to obtain samples for Therapeutic if obstructing mass
diagnosis lesions are present
Therapy Oral chemotherapy: Injectable chemotherapy:
prednisone and CHOP (cyclophosphamide,
chlorambucil; radiation doxorubicin, vincristine,
therapy may be useful to prednisone  L-asparaginase
prolong survival  methotrexate), CCNU
(lomustine), MOPP
(mustargen, vincristine,
prednisone, procarbazine);
radiation therapy may be
useful to prolong survival
Response to therapy 75%–90% response rate 50%–60% response rate
Outcome Most cats live >2 years and are Median survival 6–7 months; if
managed long term with complete response to
chemotherapy therapy 40% chance of living
a year or longer
 Alimentary Lymphoma in Cats and Dogs 421

hepatomegaly, an abdominal mass consisting of mesenteric lymph nodes or an intra-

mural mass, and/or diffusely thickened intestinal loops.3

Diagnosis of Lymphoma
Lymphoma should be suspected in cats with thickened intestinal loops, mesenteric
lymphadenopathy, intestinal masses, or multicentric organ infiltration. For cats with
a history of gastrointestinal illness, weight loss, or hyporexia/anorexia, a thorough
workup to identify primary and concurrent diseases is indicated. Baseline bloodwork
including a complete blood count (CBC), chemistry panel, thyroid function testing, and
urinalysis is essential. Testing for FeLV and FIV is generally indicated in any sick cat.
For cats with suspected neoplasia, 3-view (ventrodorsal or dorsoventral, right and left
lateral views) thoracic radiographs should be obtained to rule out gross metastatic
disease. Abdominal radiography can be helpful to evaluate cats for the presence of
abdominal masses, GI outflow tract obstruction, organomegaly, and constipation.
Abdominal ultrasonography is indicated to evaluate intestinal wall thickness, to docu-
ment the presence of GI outflow tract obstructions, to identify mass lesions and
changes in liver/spleen parenchyma, and to evaluate mesenteric lymph nodes.
CBC abnormalities in cats with GI lymphoma may include anemia (usually nonrege-
nerative anemia of chronic disease or regenerative anemia secondary to intestinal
blood loss) and neutrophilia (secondary to inflammation, neoplasia, or stress).
Biochemical abnormalities may include hypoalbuminemia and/or panhypoproteine-
mia secondary to intestinal loss; in one study, 49% of cats with LL and 50% of cats
with LBL were hypoalbuminemic.3 Increased liver enzymes may indicate hepatic
lymphoma or concurrent liver disease (hepatic lipidosis, cholangiohepatitis). Bone
marrow aspiration and cytology is recommended as part of systemic staging for
lymphoma in cats that are FeLV positive or in cats with cytopenias or circulating malig-
nant lymphocytes. Polymerase chain reaction (PCR) of the bone marrow for detection
of FeLV should be considered if a bone marrow aspirate is obtained.
Because the ileum is the sole site of cobalamin (vitamin B12) absorption, low serum
cobalamin concentrations support a diagnosis of primary intestinal disease in cats
with normal exocrine pancreatic function. In addition, determination of serum feline
pancreatic lipase immunoreactivity may be useful, as the clinical signs of feline
pancreatitis may be difficult to distinguish from those of GI lymphoma.
Ultrasound findings in cats with LL are usually indistinguishable from those with
inflammatory bowel disease (IBD), and consist of normal or increased intestinal wall
thickness with preservation of intestinal layers.2,9 Mesenteric lymphadenopathy,
intestinal intussusceptions, or distinct intramural mass lesions may also be noted. In
a recent study evaluating differences in ultrasound findings between cats with LL
versus IBD, thickening of the muscularis propria was present in 12.5% of normal
cats, 4.2% of cats with IBD, and 48.4% of cats with LL.10 Cats with lymphoma
were 18 times more likely to have a thickened muscularis layer than were cats with
IBD (Figs. 1 and 2). Mesenteric lymphadenopathy was present in 47% of cats with
LL and 17% of cats with IBD. Of the cats with lymphoma, 26% had both muscularis
thickening and lymphadenopathy, whereas only 1 of 24 cats with IBD had this combi-
nation of findings. In another study of 16 cats with LL, mesenteric lymphadenopathy
was present on ultrasonography in 12 cats, diffuse small intestinal wall thickening in
9, and a focal intestinal mass in 1.2 The diagnostic value of cytologic evaluation of
an ultrasound-guided aspiration of enlarged mesenteric lymph nodes for confirmation
of LL was reported to be questionable: benign lymphoid hyperplasia was diagnosed in
9 of 12 cats with LL and abdominal lymphadenopathy. However, when surgical
422 Gieger

Fig. 1. Abdominal ultrasonogram of a cat with lymphocytic lymphoma (LL). The hypoechoic
small intestinal muscularis layer is diffusely thickened. Although this change is not specific, it
has been reported to occur more frequently in cats with LL as well as in cats with IBD. (Cour-
tesy of Dr L. Gaschen, Louisiana State University.)

biopsies were obtained of the affected lymph nodes, lymphoma was confirmed in 8 of
9 cases.2
Ultrasound findings in cats with LBL may include transmural intestinal thickening,
disruption of normal wall layering, reduced wall echogenicity, localized hypomotility,
abdominal lymphadenomegaly, and mass lesions (Fig. 3).10 Concurrent liver involve-
ment may also be present, as evidenced by a hyperechoic or hypoechoic liver.
Pancreatic and splenic involvement may also be noticed. The presence of diffuse
echogenicity changes and/or nodular lesions in these organs supports possible infil-
tration with lymphoma.10
The optimal approach to definitively diagnosing feline GI lymphoma varies among
clinicians. Fine-needle aspiration and cytology of intestinal masses, enlarged mesen-
teric lymph nodes, or the liver may be diagnostic for lymphoma, and are relatively
noninvasive and rapid diagnostic methods. However, the presence of inflammation
and/or lymphoid reactivity may hinder a definitive diagnosis, and histopathology of

Fig. 2. Moderately thickened jejunal segment with transmural loss of layering in an older
cat with lymphocytic lymphoma. (Courtesy of Dr L. Gaschen, Louisiana State University.)
 Alimentary Lymphoma in Cats and Dogs 423

Fig. 3. Large jejunal mass of 3.84 cm diameter with transmural loss of layering in a vomiting
cat with lymphoblastic lymphoma. (Courtesy of Dr L. Gaschen, Louisiana State University.)

tissue biopsies may be necessary to confirm the diagnosis of lymphoma. Controversy

exists regarding whether endoscopically or surgically obtained intestinal biopsies are
most helpful to differentiate feline IBD from GI lymphoma.

Surgically versus endoscopically obtained intestinal biopsies

The obvious advantage of surgically obtained biopsies is that they are transmural and
therefore include all of the layers of the GI tract, allowing the pathologist to evaluate
the disease process thoroughly. In addition, the clinician can obtain biopsies of the
mesenteric lymph nodes, liver, and pancreas during the laparotomy. Disadvantages
of surgery include longer anesthesia time and a more invasive procedure followed
by a period of wound healing in an often debilitated cat. In a recent study of 43 cats
with chronic signs of illness related to the GI tract, full-thickness biopsies were
obtained.11 Twenty-three percent of cats were diagnosed with LL; the majority of
cats had IBD (46.5%), and fewer cats had fibrosis (9.3%), gastritis (7%), lymphangiec-
tasia (7%), and mast cell tumors (4.7%).
In a study of 17 cats with LL diagnosed via full-thickness GI biopsies, lymphoma
was detected in the stomach (33%), duodenum (83%), jejunum (100%), ileum
(93%), mesenteric lymph nodes (59%), liver (27%), colon (20%), and pancreas
(7%); however, not all sites were biopsied in all cats.2 All but one cat had lymphoma
present in multiple biopsied sites and in 4 cats, IBD was present in other parts of
the intestinal tract. Concurrent GI tract diseases including chronic pancreatitis (n 5 1),
neutrophilic cholangitis (n 5 1), and hepatic lipidosis (n 5 1) were also diagnosed.
The advantage of endoscopic biopsy is that it is a less invasive, shorter procedure
that is often better suited to a critically ill feline than is exploratory laparotomy. Further-
more, it allows visualization of the mucosa, which helps to identify the best sites for
collection of biopsies. The skills and persistence of the endoscopist are critical in
obtaining diagnostic samples. In a recent study,12 “marginal” duodenal biopsy
samples were defined as samples with the presence of at least one villus plus subvil-
lous lamina propria, and “adequate” samples had at least 3 villi and subvillous lamina
propria that extended to the muscularis mucosa. If 6 marginal or adequate samples of
the feline stomach or duodenum were obtained, the correct histologic diagnosis was
very likely to be achieved. Once endoscopic biopsies are obtained, sample handling to
properly orient the samples for the pathologist is critical for optimal interpretation.
The disadvantage of endoscopy is that biopsies are limited to the gastric, duodenal,
ileal, and colonic mucosa. In addition, detection of lymphoma in deeper tissues
424 Gieger

(submucosal/muscularis/serosal layers) is often difficult because of the limited depth

of the biopsy specimen. A study of 22 cats (12 with IBD and 10 with LL) examined
differences in histopathology results between endoscopic biopsy samples that had
been collected immediately before exploratory laparotomy and full-thickness GI
biopsy specimens collected during the surgical procedure.13 Of the 10 cats diagnosed
with LL, full-thickness surgical biopsies revealed jejunal and ileal involvement, and 9 of
10 had duodenal involvement. Lymphoma was also detected in the mesenteric lymph
nodes, the liver, or both. Evaluation of gastric biopsies revealed no significant differ-
ence in the ability to diagnose lymphoma between full-thickness and endoscopically
obtained biopsies. Because the pylorus could not be passed in 8 of 22 cats because
of the large size of the endoscope (chosen in an attempt to obtain large biopsy spec-
imens), one-third of the duodenal biopsies had to be obtained blindly (with collection
of only 3 samples per cat). When comparing the method used to obtain duodenal
samples, 9 cats were diagnosed with LL via full-thickness biopsies and only 1 was
definitively diagnosed via endoscopy. The study clearly demonstrates that the subop-
timal endoscopic technique has a significant impact on the diagnostic accuracy of the
method; however, it does not evaluate the diagnostic value of a thorough duodeno-
scopy with sampling of adequate numbers of good-quality samples. Overall, it under-
scores the fact that the quality of the endoscopist’s work significantly influences the
diagnostic value of upper GI endoscopy.
In some veterinary clinics, the use of laparoscopy has largely replaced the need for
laparotomy.14 This less invasive technique has many of the advantages of laparotomy,
with a significantly shorter recovery period.

Histopathologic evaluation of biopsy specimens

Histologically, IBD is characterized by a diffuse infiltration of various proportions of
lymphocytes, plasma cells, eosinophils, neutrophils, and/or macrophages that are
primarily found in the mucosal layer of the intestine. Lymphoma causes mucosal infil-
tration by neoplastic lymphocytes that are often irregularly distributed between and
among intestinal villi, with frequent progression to submucosal and transmural infiltra-
tion (Fig. 4).11,15 Lymphoma is not associated with mucosal edema or inflammation
that typically occurs with IBD.2,3 LL and LGL typically consist of T cells, and LBL

Fig. 4. Section of the duodenal mucosa of an 11-year-old male neutered Siamese cat with an
8-month history of chronic diarrhea and intermittent vomiting. There is villus blunting, and
the lamina propria is expanded by small neoplastic lymphocytes (hematoxylin-eosin stain,
original magnification 100). (Courtesy of Dr N. Wakamatsu, Louisiana State University.)
 Alimentary Lymphoma in Cats and Dogs 425

consists of B cells.2,8 Epitheliotropic intestinal lymphoma (EIL) is a subset of LL that is

characterized by infiltration of malignant T cells into the mucosal epithelium of the
intestinal tract.9 In one study,2 evidence of concurrent IBD was diagnosed in 3 of 19
cats diagnosed with LL.
The use of immunohistochemistry (IHC) for B-cell and T-cell markers may help to
distinguish IBD from LL because cats with lymphoma should have a monoclonal pop-
ulation of B or T lymphocytes (Fig. 5). In one study, of 32 cats diagnosed with LL based
on routine hematoxylin-eosin stains, 16% of cases were reclassified as having IBD,
based on a mixed population of B and T cells and plasma cells after IHC was
performed.15 Immunohistochemistry results may be difficult to interpret because
staining techniques and the antibodies used vary among laboratories, and there is
often inconsistent stain uptake in cells of an individual tumor and between tumors
from the same species. Also, the presence of T lymphocytes alone is not diagnostic
for lymphoma because of MALT (mucosal-associated lymphoid tissue), which
consists primarily of T cells and is expanded in cases of intestinal inflammation.
The use of PCR may be useful to confirm the diagnosis of GI lymphoma, because
detection of a clonal expansion of either B or T lymphocytes would be diagnostic
for lymphoma, while a mixed population of lymphoid cells supports a diagnosis of
IBD. In a study of intestinal biopsies from 28 cats with intestinal T-cell lymphoma diag-
nosed by light microscopy and IHC, 22 had clonal rearrangements of their T-cell
receptor gamma genes; this is in contrast to a polyclonal arrangement of receptors
in 9 cats with IBD.16
Treatment Options and Prognosis for Cats with Lymphoma
Surgery for cats with obstructing GI masses is indicated to relieve the obstruction and
discomfort associated with the mass. Complete resection may not be possible in
some cases, however, and dehiscence of the anastomosis site must be considered
as a possible complication. Surgical excision of intestinal masses should be followed
by biopsy of other parts of the GI tract, liver, pancreas, and mesenteric lymph nodes,
because it is rare to have a solitary mass of lymphoma with no concurrent organ
involvement. Postoperative chemotherapy is indicated because lymphoma is almost
always considered a multicentric disease, but a gold-standard protocol does not exist.
Selection of a chemotherapy protocol depends on the type of lymphoma (lymphocytic

Fig. 5. Same biopsy as in Fig. 4. The majority of neoplastic cells stain positive for CD3.
Diagnosis: T-cell lymphoma, LL (CD3 immunohistochemistry, original magnification 100).
(Courtesy of Dr N. Wakamatsu, Louisiana State University.)
426 Gieger

vs lymphoblastic), as well as patient-associated factors including concurrent disease

and owner-associated factors such as finances, ability to medicate the cat, and ability
to return for rechecks. In general, cats with LL have better responses to therapy and
longer survival times than those with LBL. In one study of cats with alimentary
lymphoma treated with various chemotherapy protocols, 50 cats with LL had
a complete response (CR) rate of 69% and a median survival time (MST) of 17 months
as compared with an 18% CR rate and an MST of 3 months for 17 cats with LBL.3
Lymphocytic lymphoma is typically a slowly progressive disease, and chlorambucil,
a chemotherapeutic agent that targets slowly dividing lymphocytes, is used along with
steroids such as prednisone or prednisolone (Table 2). There is some debate about
whether chlorambucil should be administered as a bolus dose (a single large dose
every 3 weeks) or every other day continuous dosing. Because cats will potentially
be treated with chlorambucil for several months to year(s), the clinician must deter-
mine a therapeutic plan that is suitable for both the cat and the client. The potential
advantages of the bolus-dosing regimen include (1) less owner exposure to chemo-
therapy and (2) less continuous exposure of the cat to chemotherapy.17
In one study of 42 cats with LL treated with prednisone (5–10 mg orally [PO] every 24
h) and chlorambucil (2 mg PO every 48–72 h), there was an overall response rate of
95% with a 56% CR rate (ie, 100% resolution of clinical signs and detectable tumor)
and 39% partial response (PR) rate (ie, >50% but <100% decrease in the amount of
measurable disease).8 For cats achieving a CR to therapy, the median remission dura-
tion was 897 days as compared with 428 days for cats achieving a PR. Twelve cats
died of lymphoma during the study period (median follow-up time of 476 days). Over-
all, the MST of affected cats was 704 days. In another study of 17 cats with LL treated
with either prednisone (1–2 mg/kg PO every 24–48 hours) and chlorambucil (15 mg/m2
PO every 24 hours for 4 consecutive days every 3 weeks) or a multidrug injectable
chemotherapy protocol (including vincristine, cyclophosphamide, doxorubicin, and
L-asparaginase), the CR rate was 76% with a median remission duration of 19 months
(range, 3.5–73 months).2
In one study of 28 cats with LL (24 were diagnosed via full-thickness biopsy) treated
with prednisone and chlorambucil, the clinical response rate was 96%.17 In this study,
IHC confirmed that 94% of cases were of T-cell origin. Rescue therapy with cyclo-
phosphamide was successful in 7 of 9 cats that developed recurrence of clinical signs
of their of their disease during treatment with chlorambucil (complete restaging was
not always performed). The median duration of clinical remission was 786 days. Of
interest, 4 of 28 cats developed a second, unrelated malignancy.
There are few studies that address rescue chemotherapy for cats with LL, because
many cats do not develop clinical relapse and survival times are typically long
(Table 3). Cyclophosphamide has been used as a rescue therapy, with good
responses.17 Other drugs typically used to treat LBL including (but not limited to)
vincristine, vinblastine, doxorubicin, and L-asparaginase could be used to attempt
reinduction of clinical remission. Additional considerations for cats with recurrent clin-
ical signs include repeat staging (ultrasonography, endoscopy) to look for new concur-
rent diseases and/or the progression of LL to the lymphoblastic form; this has not been
well described, however.
Because cats with LBL are often severely ill at the time of diagnosis, intensive
supportive care in addition to chemotherapy is warranted. This treatment may include
intravenous (IV) fluid therapy, blood products, IV antibiotics, and enteral or parenteral
nutrition. For cats with LBL, multidrug protocols are the most widely studied, and
COP (cyclophosphamide, vincristine, prednisone) or CHOP (cyclophosphamide, doxo-
rubicin, vincristine, prednisone  L-asparaginase  methotrexate) based protocols
 Table 2
Chlorambucil D prednisone chemotherapy protocols for cats with lymphocytic lymphoma

Chlorambucil Dose Median Response Median Survival

(PO) Prednisone Dose (PO) Response Rate Duration (months) Time (months) Comments References
8
2 mg every 48–72 h 5 or 10 mg/cat/d 56% CR 30 mo if CR n/a
39% PR 14 mo if PR
15 mg/m2 every 24 h  4 d 3 mg/kg every 24 h then 76% CR 19 mo 19 mo if CR; 2

every 3 wk 1–2 mg/kg when 4 mo if not CR

remission is achieved
15 mg/m2 every 24 h  4 d 3 mg/kg every 24 h then 69% CR 16 mo 17 mo overall; 3

Alimentary Lymphoma in Cats and Dogs

every 3 wk 1–2 mg/kg when 23 mo if CR
remission is achieved
20 mg/m2 every 2 wk Variable 96% CR 26 mo Good response to 17

(round to nearest 2 mg cyclophosphamide

tablet size) when clinical relapse
occurred

Abbreviations: CR, complete response (100% of clinically evident disease resolved); n/a, no data available; PO, by mouth; PR, partial response (>50% but <100% of
clinically evident disease resolved).

427
 428
Table 3

Gieger
Chemotherapy protocols for cats with lymphoblastic lymphoma

Median Response Median Survival

Drugs Response Rate Duration (months) Time (months) Comments References
3
CHOP 18% CR n/a 2.7 mo Part of a larger study comparing lymphocytic and
lymphoblastic alimentary lymphoma
26,a,b
COP 75% CR 8 mo 9 mo If CR, 51% clinical remission rate at 1 y and 38% at 2 y;
cats that did not achieve CR usually did not live 1 y
32,a
COP 32% CR 7 mo if CR n/a n/a
18,a,b
COP or COP then n/a 3 mo if COP; 9 mo if n/a Study comparing COP to doxorubicin maintenance
doxorubicin COP then doxorubicin therapy
24,a,b
CVM 52% 4 mo n/a Addition of prednisone and L-asparaginase did not
improve results
23,a,b
CVM-L 62% CR 7 mo if CR; Cats with minimal response to therapy: MST 1.5 mo;
20% PR 2.5 mo if PR FeLV 1 worse prognosis; cats with stages I and II
lymphoma had a better prognosis
19,a,b
Doxorubicin 42% Median 2 mo; 3 mo if CR Cats with CR to therapy and FeLV-negative cats have
a better prognosis
33,a,b
Doxorubicin 22% response n/a n/a Doxorubicin used as a rescue therapy; small cell
lymphoma and cats receiving drugs in addition to
doxorubicin were more likely to respond to therapy;
not thought to be an effective rescue therapy
27,a,b
CHOP-L-M 47% CR 22 mo if CR 22 mo if CR
37% PR 4 mo if PR 4 mo if PR
25,a
CHOP-L-M n/a 5 mo 10 mo Longer duration of first remission resulted in longer
survival time
21,a,b
CHOP-L-M 74% CR 9 mo if CR 10 mo if CR 6-mo clinical remission rate 75%; 1-y clinical remission
14% PR rate 50%

Abbreviations: C, cyclophosphamide; CR, complete response (100% of clinically evident disease resolved); FeLV, feline leukemia virus; H, hydroxydaunorubicin,
doxorubicin; L, L-asparaginase; M, methotrexate; MST, median survival time; O, vincristine; P, prednisone or prednisolone; PR, partial response (>50% but
<100% of clinically evident disease resolved); V, vincristine.
a
A diagnosis of lymphoma was confirmed in these studies; however, it was not documented whether it was lymphocytic or lymphoblastic.
b
Not all cats in these studies had alimentary lymphoma.
 Alimentary Lymphoma in Cats and Dogs 429

have been shown to have better efficacy than single-agent protocols and steroids
alone.18,19 Recently, CCNU (lomustine) used as a single agent or in combination with
steroids has been shown to be effective in the treatment of feline lymphoma, and
appears to be a reasonable treatment option for many cats.20 In general, cats are
less responsive to chemotherapy than dogs when they are treated for LBL. Most studies
document response rates for cats with LBL at approximately 50% to 75% with an MST
of 7 to 9 months.21–28 One of the few consistent prognostic indicators in cats treated for
LBL is response to therapy; several studies have documented that cats that have a CR
to therapy have longer survival times than those that only have a PR to therapy.23,25
Other possible indicators of prognosis include the World Health Organization stage
of disease. Cats with stage 1 (single extranodal or lymphoid site) and stage 2 (regional
lymphadenopathy or resectable GI mass) lymphoma have longer survival times than
other stages.23 Finally, a positive FeLV antigen test is considered a negative prognostic
factor, because cats infected with this virus typically die of viral-associated syndromes
even if therapy for lymphoma is effective.21
LGL is an uncommon form of feline alimentary lymphoma that has a poor
prognosis.5 In a study of 45 cats with LGL, all cats tested negative for retroviruses.
Twenty-three cats were treated with chemotherapy. Thirty percent responded, and
the MST was 57 days (range, 0–267 days). Prognostic factors for improved survival
were not detected.
In general, cats tolerate chemotherapy very well and clinically significant neutrope-
nia is uncommon.22 In a recently published survey of 31 owners whose cats were
undergoing COP chemotherapy, 83% of owners were happy that they treated their
cats and 87% stated they would treat another cat.22
Dietary modifications should be considered as part of the treatment protocol for
cats with lymphoma. Diets should be highly digestible and palatable. For cats with
concurrent IBD, hypoallergenic diets should be considered. For cats that are anorexic
or hyporexic, enteral nutritional support should be provided by means of an esopha-
geal or gastric feeding tube. Appetite stimulants such as cyproheptadine and mirtazi-
pine may also be helpful. For many cats, once chemotherapy (including steroids) is
initiated, the appetite improves and the tube can be removed.
Parenteral cobalamin supplementation should be considered even if serum
concentrations are not measured, because the prevalence of hypocobalaminemia
in cats with GI lymphoma was reported to be 78% in one study.8 In another study
of cats with a history of clinical signs related to the GI tract and confirmed severe
hypocobalaminemia (<100 ng/L), the serum cobalamin concentrations and mean
body weight increased, and signs of GI disease improved in the majority of animals
after 4 weeks of administration of cobalamin at a dose of 250 mg subcutaneously
once weekly.26 Limitations of this study included that the cats did not have
biopsy-confirmed diagnoses of GI disease and that the majority of cats were
receiving other therapy (steroids, antibiotics) concurrently with vitamin B12
supplementation.
Radiation therapy for alimentary lymphoma may be an underutilized treatment
modality in cats, because lymphoma is generally a radiation-responsive disease.
Radiotherapy is used successfully for the treatment of solitary site lymphomas,
including nasal and spinal lymphoma. In a pilot study of 8 cats with LBL treated
with 6 weeks of standard multidrug chemotherapy followed by 10 daily 1.5-Gy
fractions of radiation, 5 of 8 cats had long-term (>266 days) progression-free
survival.29 Radiation therapy was well tolerated. Further studies are warranted
that will hopefully result in prolongation of survival times in cats with alimentary
lymphoma.
430 Gieger

CANINE ALIMENTARY LYMPHOMA

Alimentary lymphoma is less common in dogs than in cats, representing only 7% of all
canine lymphomas. Alimentary lymphoma in dogs may be part of the syndrome of
multicentric lymphoma (ie, peripheral lymph nodes  other organ systems), but
most commonly, it is confined to the GI tract.30 In one study of 18 dogs with alimentary
LBL, 13 (72%) had lymphoma confined to the intestinal tract, and lymphoma was part
of multicentric disease in the remaining 5 (28%). Unlike in cats, lymphocytic lymphoma
of the alimentary tract is rare. The majority of dogs have rapidly progressive clinical
signs associated with lymphoblastic lymphoma, including (in decreasing order of
frequency) vomiting, diarrhea, weight loss, anorexia, and lethargy.31 Physical exami-
nation findings in dogs with LBL may include ascites, poor body condition, a palpable
abdominal mass, abdominal pain, and thickened intestinal loops. Staging tests are
similar to those for feline lymphoma. The most common biochemical abnormality is
hypoalbuminemia (which occurs in 61%–80% of dogs); and hypercalcemia is
uncommon. The majority of alimentary lymphomas in dogs are of T-cell origin.30,31
Chemotherapy and supportive care are the mainstays of the treatment of alimentary
lymphoma in dogs. The overall response rate to treatment with a multidrug chemo-
therapy protocol (vincristine, L-asparaginase, cyclophosphamide, doxorubicin, pred-
nisone, lomustine, procarbazine, mustargen) was 56% in the largest published
study of dogs with alimentary lymphoma.30 For the responders, the overall median first
remission duration was 86 days and the MST was 117 days. Dogs that did not respond
to treatment were euthanized a median of 10 days after initiation of therapy. Dogs with
diarrhea as a presenting complaint had a worse prognosis, with 13 diarrheic dogs
having an MST of 70 days versus 700 days for 5 dogs without diarrhea. Similar to
cats with alimentary LBL, intensive fluid therapy and nutritional support (enteral or
parenteral) is indicated concurrently with chemotherapy in clinically ill dogs with
alimentary lymphoma.

SUMMARY

This article presents a review of feline and canine alimentary GI lymphoma. Gastroin-
testinal lymphoma should be suspected in animals with an acute or prolonged history
of clinical signs of disease related to the GI tract. Systemic staging tests (CBC/chem-
istry/urinalysis/thyroxin levels/thoracic radiographs) are used to identify concurrent
disease. Abdominal ultrasonography is useful for the documentation of intestinal
wall thickening, mass lesions, concurrent organ involvement, lymphadenopathy,
and abdominal lymphadenopathy. The ultrasonographic findings can be used to
decide whether the next diagnostic test should be laparotomy, laparoscopy, or endos-
copy, with the goal of obtaining diagnostic histologic specimens. Histopathologically,
lymphoma may be lymphoblastic or lymphocytic; these diseases have different ther-
apies and prognosis. Chemotherapy, including steroids and nutritional support, are
essential in the management of alimentary lymphoma.

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