Page 485 - Withrow and MacEwen's Small Animal Clinical Oncology, 6th Edition

CHAPTER 23 Cancer of the Gastrointestinal Tract 463

small intestinal lesions in weight loss; and large bowel lesions Clinical Pathology
in hematochezia and tenesmus. 456,458 Although carcinoids may Complete Blood Count
secrete endocrine substances, clinical signs do not always reflect
VetBooks.ir hypersecretion. 472 Dogs and cats may present with clinical signs Anemia is common in dogs and cats with intestinal tumors and
is often not characterized, but may occur in conjunction with
relating to intestinal obstruction, such as anorexia, weight loss,
and vomiting. In dogs with cecal GISTs, 25% to 32% cause melena and elevated blood urea nitrogen (BUN). Anemia affects
perforation which results in a localized peritonitis and clini- nearly 40% of dogs in most studies and as low as 15% but up
cal signs of an acute abdomen. 487,488 Smooth muscle tumors to 70% of cats. 441,445,451,452,456,458,460 Leukogram changes are also
are located within the muscular layer of the intestines and not common including leukocytosis in 25% to 70% of dogs and 40%
within the lumen and evidence of GI bleeding is often absent, of cats. 441,444,452,458 A left shift may be seen as well as monocytosis
but anemia and melena have been reported. 451,452 Clinical signs in some patients. 458,460
of chronic small bowel disease should not be ignored in cats,
as 96% to 99% had abnormalities on biopsy consistent with Chemistry Profile
inflammatory bowel disease (IBS) or neoplasia (lymphoma, Biochemical abnormalities are similar between dogs and cats
MCT, adenocarcinoma). 507,508 with intestinal tumors. As a result of malabsorption, hypopro-
teinemia may be present in one-fourth to one-third of patie
Paraneoplastic Syndromes nts. 441,444,445,452,453,456 Other common abnormalities include
elevated liver enzymes, specifically alkaline phosphatase in 15% to
One dog was presented for alopecia and Cheyletiella infection 33% of dogs and up to 85% of cats with nonlymphomatous neo-
within 2 months of euthanasia for abdominal carcinomatosis plasia. 441,452,456,458,460 In one series, high cholesterol was seen in
from intestinal carcinoma. The neoplasia was not identified with 41% of cats with nonlymphomatous tumors. 458 An elevated BUN
abdominal US at the original workup, but immunosuppression has been reported in 13% of dogs and 30% of cats with intestinal
resulting from an underlying neoplasia was thought to lead to adenocarcinoma. 441,444 This may be a result of concurrent renal
opportunistic Cheyletiella infection. Although pruritus resolved insufficiency, intestinal bleeding due to the tumor, or dehydra-
with ivermectin therapy, alopecia persisted, suggesting a paraneo- tion. Although some cats may have hyperglycemia, 458 smooth
plastic origin. 509 Alopecia has also been reported as a paraneo- muscle tumors can cause up to 55% of patients to be hypogly-
plastic syndrome secondary to a metastasizing colonic carcinoma cemic as a result of insulin-like growth factor secretion. 451 Dogs
in a cat. 510 Neutrophilic leukocytosis (in one dog associated may also have increased amylase and electrolyte disturbances, 456
with monocytosis and eosinophilia) has been reported in dogs and patients with lymphoma may be hypercalcemic. 445 Serum
with rectal tumors. Resolution or improvement of hematologic alpha 1-acid glycoprotein, an acute-phase reactant protein, may
abnormalities occurred after treatment for adenomatous rectal be increased in cats with cancer, but this lacks specificity and prog-
polyps. 502,511 Hypereosinophilia and eosinophilic tumor infil- nostic relevance. 519,520
trates have been reported in a cat and several dogs with intestinal
T-cell lymphoma; the suggested cause was IL-5 secretion by the Cytology and Histopathology
neoplastic lymphocytes. 512–514 EMP may lead to a hyperviscosity As with other anatomic sites, cytology of the intestinal tract can
syndrome resulting from overproduction of immunoglobulin. 515 help differentiate major tumor types. In addition, lymphocyte
Erythrocytosis managed with periodic phlebotomy was related accumulations can be tested using polymerase chain reaction
to a cecal leiomyosarcoma in a 14-year-old dog. The diagnosis (PCR) for antigen receptor rearrangement (PARR) for clonal-
was made at postmortem 2 years later; erythropoietin mRNA ity (see Chapter 33, Section A and B for further details). In cats,
and protein were isolated from tumor cells, suggesting ectopic mucosal biopsies of the upper GI tract are commonly obtained in
erythropoietin production as the cause of the erythrocytosis. 516 a minimally invasive fashion using endoscopy. Despite the supe-
Hypoglycemia has also reported with intestinal smooth muscle riority of full thickness biopsies (because submucosal and mus-
tumors as a paraneoplastic syndrome. 517 Nephrogenic diabetes cularis infiltration can be characterized), the ease of endoscopic
insipidus has also been documented in one dog with intestinal biopsy has resulted in rigorous evaluation of ancillary diagnostics
leiomyosarcoma. 518 to improve accuracy on these samples. Because of reported eosino-
philia with intestinal lymphoma and reports of MCT with con-
Diagnostic Techniques and Workup current small T-cell lymphoma in cats, it may be challenging to
512,521,522
distinguish between the two tumor types.

Physical Examination
Imaging
An abdominal mass may be palpated on initial examination in
approximately 20% to 40% of dogs with lymphoma 450,453 and Abdominal Radiographs and Ultrasound
20% to 50% of dogs with nonlymphomatous solid intestinal In dogs and cats with intestinal lymphoma, concurrent enlarge-
tumors. 441,456,458 Pain and fever were reported in 20% of dogs ment of liver, spleen, and/or mesenteric LNs may be seen. 450
with lymphoma in one report. 450 Digital rectal examination Plain abdominal radiographs may reveal an abdominal mass
may identify masses or annular strictures due to rectal tumors in approximately 40% of both dogs and cats, although some
or polyps in as high as 63% of dogs. 456,474 Abdominal masses reports are higher for solid tumor types and lower for lym-
are also often readily palpated in cats with both lymphoma and phoma. 441,444,445,450,452,458 An obstructive pattern may also
adenocarcinoma. 444,445,458,460 Dehydration is also common be seen on plain radiographs in 10% to 75% of cats and
and occurs in 30% to 60% of cats with nonlymphomatous dogs. 441,452,456,458 Other abnormalities may include poor serosal
tumors. 444,458 detail and thickened stomach wall. 445