Page 1351 - Clinical Small Animal Internal Medicine

142 Cancer of the Small and Large Intestine 1289

adenocarcinoma is 10–11 years. Siamese may be over- serum electrophoresis, bone marrow aspiration/evalua-
VetBooks.ir represented. Feline intestinal mast cell tumors tend to tion, abdominal ultrasound, and survey skeletal radio-
graphs. In cats with intestinal lymphoma or intestinal
affect older cats with a mean age of 13 years. Feline
colonic adenocarcinoma generally affects older cats with
50% of cases. Abdominal radiographs may show an
no discernible sex or breed predilection. carcinoma, an abdominal mass can be palpated in over
obstructive pattern or abdominal mass. Three‐view tho-
racic radiographs should be performed but are usually
History and Clinical Signs negative for metastasis at the time of diagnosis.
The imaging test that will give the clinician the most
Clinical signs for most small intestinal neoplasias in dogs useful information is abdominal ultrasound which pro-
and cats are similar and include one or more of the vides information regarding size and location of the mass
following: anorexia, vomiting, diarrhea, weight loss, as well as evidence of metastatic spread. It also provides a
melena, and lethargy. Signs may be subacute, acute or means to achieve a diagnosis through less invasive proce-
chronic in nature, depending on the underlying disease dures such as ultrasound‐guided aspiration and ultra-
process. A patient may present with acute vomiting, ano- sound‐guided biopsy. Ultrasound‐guided aspirates and
rexia, and abdominal discomfort secondary to a gastric biopsies both can result in a false negative if a cystic,
or small intestinal obstructive lesion or with a history of necrotic or inflammatory area of the tumor is sampled.
chronic weight loss, decreased appetite and intermittent As with any neoplasia, biopsy and histopathology is
vomiting over the course of months if a low‐grade intes- the preferred method of diagnosis. Occasional misdiag-
tinal lymphoma is the underlying problem. Therefore, nosis of neoplasia can occur with aspiration/cytology,
the chronicity of signs should not dissuade the clinician where a tumor may be aspirated and the cytology is con-
from keeping neoplasia on the differential list for many sistent with one type of neoplasia (i.e., carcinoma) but
common GI presentations. Some patients may present in when a biopsy and histopathology are performed, the
shock if a GI perforation occurs secondary to underlying diagnosis changes to another tumor type (i.e., lym-
intestinal neoplasia. Dogs with intestinal leiomyosarco- phoma). This can occur when the aspiration contains
mas may present with signs secondary to paraneoplastic cells which are not representative of the underlying
hypoglycemia, such as weakness, ataxia, and seizures. lesion, the tissue sampled does not exfoliate well or in
Some patients with intestinal tumors may present with order to make a correct diagnosis of neoplasia the evalu-
signs referable to anemia such as weakness and lethargy ation of the tissue architecture is needed, not just evalu-
secondary to gastrointestinal bleeding. ation of the cell type. Endoscopy and colonoscopy may
be helpful in diagnosing proximal small intestinal lesions
and colorectal lesions respectively. However, endoscopic
Diagnosis biopsy may underdiagnose intestinal lymphoma in dogs
and cats. Ultimately, abdominal exploratory surgery with
A complete blood count, biochemistry profile, and uri- either incisional or excisional biopsy and histopathology
nalysis are recommended as part of a minimum database may be necessary to obtain a definitive diagnosis.
but are not helpful in establishing a definitive diagnosis. Immunohistochemistry for the expression of c‐kit
Anemia can be seen in up to ~64% of dogs with intestinal (CD117) is recommended in dogs with intestinal sarco-
neoplasia and is associated with intestinal hemorrhage mas to differentiate between GISTs (CD117 positive)
or anemia of chronic disease. and leiomyosarcoma (CD117 negative). The differentia-
The chemistry panel can reveal a paraneoplastic tion between GISTs and leiomyosarcomas can have both
hypoglycemia in dogs with intestinal leiomyosarcoma. prognostic and therapeutic implications.
When a dog presents primarily for signs secondary to Routine immunohistochemistry has identified that T
hypoglycemia, rather than gastrointestinal signs, a serum cell is the most common immunophenotype of intesti-
sample should be held for simultaneous blood glucose nal lymphoma in dogs. Feline intestinal lymphoma can
and blood insulin levels to rule out inappropriate insulin be either T cell or B cell in origin.
secretion secondary to an insulinoma (beta‐cell tumor of
the pancreas). Hypoproteinemia is a common laboratory
finding secondary to malabsorption or intestinal loss Therapy
in dogs and cats with diffuse intestinal lymphoma.
Cobalamin and folate should be assessed to evaluate for Surgical excision via intestinal resection and anastomo-
malabsorption and small intestinal bacterial overgrowth. sis, with or without adjuvant chemotherapy, is the
Animals with intestinal extramedullary plasmacytomas primary treatment for most animals with intestinal neo-
should be thoroughly staged for systemic disease with plasia. Intestinal lymphoma is the one notable exception,