Page 742 - Withrow and MacEwen's Small Animal Clinical Oncology, 6th Edition

720 PART IV Specific Malignancies in the Small Animal Patient

infiltration patterns with the WHO classification scheme 493 as well occur with malignant pleural effusion and a mediastinal mass
as documenting anatomic location, cell size, presence of epithe- present. Peripheral blood involvement was present in 10% to 15%
and as often as 86% in another report.
in some reports
438,500
liotropism, clonality, and outcome data. This information is sum-
501
VetBooks.ir marized in Table 33.10. Of the 120 cases, none tested serologically Affected cats are generally FeLV/FIV negative.
positive for FeLV and only three cats tested positive for FIV. Four
cats had large B-cell lymphoma (gastric, cecal, or colonic) con- History, Clinical Signs, and Physical
current with small T-cell lymphoma of the small intestine. Topo- Examination Findings
graphically, T-cell variants are much more likely to occur in the
small intestine (94%) and rarely in the stomach or large intestine. Low-Grade Alimentary Lymphoma
The majority of T-cell variants are mucosal (equivalent to WHO LGAL is most commonly associated with nonspecific signs associ-
enteropathy-associated T-cell lymphoma [WHO EATCL] type ated with the GI tract; most cats present with weight loss (>80%),
II), and the majority of B-cell tumors are transmural (equivalent vomiting and/or diarrhea (70%–90%), and hyporexia (70%–
to WHO EATCL type I classification). Regarding cell size, nearly 90%), whereas icterus is uncommon (7%). 436,486,503,504 Abdomi-
all mucosal T-cell tumors were composed of small lymphocytes, nal palpation is often unremarkable, but intestinal thickening,
and slightly more than half of transmural T-cell and all B-cell vari- mesenteric lymphadenopathy, and organomegaly can occasion-
ants were composed of larger cells. Epitheliotropism is common ally be appreciated. Clinical signs are usually present for several
with LGAL T-cell tumors, but is rare in B-cell tumors. Other months before diagnosis (median, 6 months). 504
abdominal organ involvement is common, and in one report of
29 cases of low-grade T-cell intestinal lymphoma, liver and mes- Intermediate- or High-Grade Alimentary Lymphoma
enteric node involvement was documented in 53% and 33% of I/HGAL tends to cause similar clinical signs as LGAL; however,
cases, respectively. 494 Hepatic lymphoma can occur concurrently they tend to progress more acutely and are more likely to present
with GI lymphoma or be confined solely to the liver. 486,495 Most with a palpable abdominal mass originating from the GI tract,
are T-cell and clonal or oligoclonal based on PCR analysis. enlarged mesenteric lymph nodes, or liver. 436,439,461,496,503,505
Icterus is also more common in large cell forms. Hematochezia
Intermediate- or High-Grade Alimentary Lymphoma and tenesmus may also be present if the colon is involved. 459
Unlike LGAL, the majority of I/HGALs are large or intermediate Rarely, cats may present with signs consistent with an acute abdo-
sized B-cell lymphomas. They arise from organized lymphoid tis- men due to intestinal obstruction or perforation and concurrent
sues; MALT in the stomach and Peyer’s patches and mucosal lym- peritonitis.
phoid nodules concentrated in the distal small intestine, cecum,
and colon. 436,487,488,496,497 Therefore I/HGAL is more common Large Granular Lymphoma
in the stomach, distal small intestine, cecum, and colon (see Cats with intestinal LGL have typical GI clinical signs, but are also
Table 33.10). These B-cell variants can be solitary or at multiple more likely to be acutely presented. 438,498,500,501 A palpable abdomi-
sites that occur simultaneously within the stomach, small intes- nal mass is present in approximately half of cases, and hepatomeg-
tine, and ileocecocolic junction. The majority are transmural aly, splenomegaly, and renomegaly are common. Abdominal and
(equivalent to WHO EATCL type I classification) and epitheliot- pleural effusions, and icterus are observed in nearly 10% of cases.
ropism is rarely observed.
Large Granular Lymphoma Diagnosis and Clinical Staging
LGL represents a less common, distinct form of alimen- For most cats with suspect alimentary/GI lymphoma, the diagnos-
tary lymphoma occurring in older (median age 9–10 years) tic evaluation should include a baseline assessment consisting of
cats. 436,438,487,497–501 These granulated round cell tumors have a CBC with differential cell and platelet count, serum biochem-
also been termed globule leukocyte tumors, although they are likely istry profile, urinalysis, and retroviral (FeLV/FIV) screen. Anemia
variations of the same disease. LGL is characterized by lympho- and neutrophilia are common findings in all forms of alimentary
cytes described as 12 to 20 μm in diameter with a round, clefted, lymphoma; however, they tend to be more profound in I/HGAL
or cerebriform nucleus, variably distinct nucleoli, finely granular and LGL. 436,438,488,498 Circulating neoplastic lymphocytes are rare
to lacey chromatin, and a moderate amount of basophilic granular with LGAL, but may be observed in up to 15% of I/HGAL and
cytoplasm that is occasionally vacuolated. 500 Prominent magenta LGL. Serum biochemistry profiles can help establish the overall
or azurophilic granules are characteristic (Fig. 7.34, Chapter 7). health of the animal and suggest extra-GI involvement (e.g., liver
They are usually granzyme B positive by immunohistochemis- enzymes elevations/icterus may indicate hepatic infiltration; azo-
try. 487 This population of cells includes cytotoxic T cells and occa- temia may indicate renal involvement). For cats with alimentary
+
−
+
sionally NK cells: most are CD3 , CD8 , and CD20 and have lymphoma, hypoproteinemia and anemia are reported to occur in
T-cell receptor gene rearrangements. 487,501 In one report, nearly up to 23% and 76% of cases, respectively. 461,486,506 Hypercalcemia
60% expressed CD103 (integrin alpha E). 501,502 LGL was con- is rarely seen in cats, but has been reported in cats with lymphoma
fined to the intestines in 93% of cases in a large compilation, 438 at various anatomic sites. Hypoglycemia, hypoalbuminemia,
but can occur extraabdominally (e.g., nasal). 438,498 Approximately hyperglobulinemia, abnormal serum folate (high or low), elevated
10% express neither B- or T-cell markers and are thus classified lactate dehydrogenase (LDH), and hypocobalaminemia are often
as NK cells. These NK tumors commonly originate in the small reported. 436,438,506,507
intestine, especially the jejunum, are transmural, often exhibit epi-
theliotropism, and at least two-thirds present with other organs Low-Grade Alimentary Lymphoma
involved; most with mesenteric lymph node involvement and LGAL must be differentiated from LPE, which have similar clini-
many with liver, spleen, kidney, peritoneal malignant effusions, cal presentations and histologic cell populations. 441,487–491,508
and bone marrow infiltration. Also, thoracic involvement may LGAL is more commonly associated with modest (or palpably