Page 473 - Withrow and MacEwen's Small Animal Clinical Oncology, 6th Edition

CHAPTER 23 Cancer of the Gastrointestinal Tract 451

The prognosis for dogs and cats with esophageal carcinomas Diagnostic Techniques and Workup
seems to be poor, as most tumors are unresectable. 243,250 The prog- Most hematologic and biochemical evaluations are nonspecific,
nosis for dogs with esophageal leiomyomas after marginal excision
VetBooks.ir appears to be good in a small case series of three dogs 248 and an but may include mild anemia, hyperglycemia, neutrophilia,
256
243
although local recurrence was reported
and bilirubinemia (if occluding the common bile duct).
additional case report,
in one dog. Similarly, dogs with low-grade leiomyosarcomas had Elevations of serum amylase and lipase are inconsistent. 269
good long-term resolution of clinical signs after marginal excision, In extreme cases, signs of pancreatic insufficiency may be
despite incomplete histologic margins in three of four dogs. 242 exhibited. 270
In the dog, most tumors are not palpable through the abdomi-
Comparative Aspects nal wall. In the cat, late-stage, large palpable masses may be
present.
A high mortality rate is associated with esophageal cancers in Positive-contrast upper GI radiographs may reveal slowed
humans. 254 The American Cancer Society predicts that 17,290 gastric emptying and occasionally compression or invasion of
new cases of esophageal cancers will occur in 2018, causing the duodenum. Ultrasonography should be a useful diagnostic
15,850 deaths. 254 The most common esophageal cancer in the tool for localization of the primary tumor, documentation, and
United States of America is adenocarcinoma followed by squa- aspiration of fluid, as well as metastasis to liver and regional
mous cell carcinoma. 254 Adenocarcinoma has a predilection for LNs. 271 Ascites may be a clinical sign and, when present, may
the distal esophagus. 255 Risk factors include obesity, male gender, reveal malignant cells on cytologic examination (carcinomato-
alcohol and tobacco consumption, gastroesophageal reflux, and sis). A large (>2 cm) solitary mass is suggestive of pancreatic
Barrett esophagus. 255 Barrett esophagus consists of metaplasia of cancer rather than nodular hyperplasia in cats. 272 Contrast ultra-
the esophageal mucosa secondary to severe gastroesophageal reflux sound has been assessed for distinguishing between pancreatic
and may be a preneoplastic lesion. 255 adenocarcinoma or insulinoma in four dogs. 273 In B-mode ultra-
sound, a hypoechoic nodule was present in the pancreas in three
dogs, whereas heterogeneous pancreatic tissue was evident in
SECTION D: EXOCRINE PANCREATIC CANCER the other dog. Contrast ultrasound could differentiate between
the two tumors: adenocarcinomas appeared as hypoechoic and
hypervascular lesions whereas insulinomas showed uniformly
LAURA E. SELMIC hypervascular lesions. 273 The utility of advanced imaging such
as CT and MRI has not been documented for exocrine pancre-
Incidence and Risk Factors atic tumors in veterinary patients. At present, most diagnoses are
made at exploratory celiotomy. Immunohistochemical markers
Cancer of the exocrine pancreas is very rare (<0.5% of all cancers) have been evaluated for aiding diagnosis of pancreatic carcinoma
in the dog and the cat. 256,257 Incidence rates of pancreatic cancer in dogs. More specifically, the expression patterns of claudin-4, a
have been estimated at 17.8 per 100,000 patient years for dogs tight junction molecule, and claudin-5, an endothelium specific
and 12.6 per 100,000 patient years for cats. 258 Older female dogs tight junction protein, were compared between well-differenti-
and spaniels have been described as being at higher risk. 259–261 ated and poorly differentiated pancreatic acinar cell carcinomas
Experimentally, N-ethyl-N′-nitro-N-nitrosoguanidine has been and normal pancreatic tissues. 274,275 Claudin-4 was present lat-
shown to induce pancreatic duct adenocarcinoma when adminis- erally in normal pancreatic acinar cells and intense apical lateral
tered intraductally in dogs. 262 position in cells from a well-differentiated exocrine pancreatic
carcinoma. Poorly differentiated exocrine pancreatic adenocar-
Pathology and Natural Behavior cinomas demonstrated a loss of claudin-4 expression. 274 The
authors concluded claudin-4 immunohistochemistry may be
Almost all cancers of the pancreas are epithelial and most are malig- useful to distinguish well-differentiated and undifferentiated
nant adenocarcinoma of ductular or acinar origin. Nodular hyper- exocrine pancreatic carcinomas. 274 Claudin-5 has also been
plasia is a common asymptomatic finding in older dogs and cats. evaluated in this manner with expression documented in lateral
Benign pancreatic pseudocysts and adenomas have been diagnosed membranes of exocrine acinar cells and the endothelial cells of
by ultrasonography or surgery in dogs and cats. 256,263 In the vast vessels and lymphatics within the stroma of the intact pancreas.
majority of cases, malignant pancreatic cancer has metastasized to The well- and poorly differentiated carcinomas showed loss of
regional or distant sites before a diagnosis can be made. 260,264 claudin-5 expression. 275

History and Clinical Signs Therapy

The history and clinical signs of exocrine pancreatic cancer are Most non–islet cell carcinomas of the pancreas are locally
vague and nonspecific and may mimic or be accompanied by invasive and metastatic to regional LNs and liver at diagno-
pancreatitis. Weight loss and anorexia (marked in cats), 265 para- sis. If liver, peritoneal cavity, or draining LNs are positive for
neoplastic alopecia in cats, 266,267 vomiting, rare associated dia- tumor, aggressive surgery should generally not be performed.
betes mellitus, 265,268 abdominal distension due to a mass effect Total pancreatectomy or pancreaticoduodenectomy (Whip-
or abdominal effusions secondary to tumor implantation on the ple’s procedure) have been described in humans and dogs, 276
peritoneum (i.e., carcinomatosis; common in cats), icterus (with but carries a high operative morbidity and mortality with-
common bile duct obstruction), and lethargy are common symp- out significant cure rates and is not recommended. Bypass
toms. 265 Alternatively, patients may present for symptoms of met- procedures, such as gastrojejunostomy or cholecystoduode-
astatic disease. nostomy, are short-term palliative options for patients with