Exocrine Pancreatic Neoplasia - Dogs and Cats

Primary pancreatic tumours are rare (accounting for less than 0.5% of all cancers in the dog), however the pancreas is also a site for metastasis from particularly gastro-intestinal neoplasms. Primary tumours include:

Carcinomas
Adenocarcinomas
Adenomas

It is important to make the distinction between pancreatic neoplasia and pancreatic nodular hyperplasia which frequently occurs in older dogs and cats and is non-significant.

Signalment

Carcinomas:

Usually female dogs with a mean age of 10 years
Spaniels and Airedale terriers may have breed predispositions
Affected cats have a mean age of 12 years

Description

Aetiology is idiopathic. Adenomas, although they do not metastasise and are frequently small and focal they can compress the surrounding pancreas. Carcinomas are aggressive with local invasion of the stomach or duodenum and metastasis to the liver, regional lymph nodes (hepatic and splenic), lungs, periotoneal surface and other abdominal organs usually occurring prior to a diagnosis being reached. Other complications include blockage of the common bile duct and exocrine pancreatic insufficiency. Pancreatitis can also occur where pancreatic atrophy results in tumour necrosis and an inflammatory response.

Diagnosis

Clinical Signs

Non-specific including:

Lethargy
Weight loss - marked in cats
Anorexia - marked in cats
Vomiting
Diarrhoea
Constipation
Abdominal pain/distension due to mass effect or abdominal effusions
Jaundice - if biliary obstruction
Alopecia - as a paraneoplastic syndrome, occurring ventrally, facially and on the limbs in cats with adenocarcinoma

Such signs may also occur with concurrent pancreatitis. Alternatively clinical signs may reflect those of metastatic disease.

Physical Examination

In cats, a mass may be palpable in the abdomen

Haematology and Biochemistry

Potential abnormalities include:

Mild anaemia
Neutrophilia
Elevated hepatic enzymes or bilirubinaemia - if there is cholestasis or biliary obstruction
Hyperglycaemia - If there is concurrent beta cell destruction
Hypokalaemia

Plain and Contrast Radiography

Plain abdominal radiography may reveal a mass or mottled appearance on account of local peritonitis. In addition, there may be diplacement of the descending duodenum and pylorus. Where there is peritoneal metastasis and effusion loss of serosal detail and increased radiodensity may be observed. Thoracic radiography is also advised for pulmonary metastases.

Positive contrast radiography can be used to evaluate gastric emptying which can be delayed with pancreatic neoplasia. Compression or invasion of the duodenum may also be seen.

Ultrasonography

Provides information on the extent of the tumour and its invasiveness. A guided fine needle aspirate may be taken at this time, however, cytological examination is often unrewarding as pancreatic tumour cells do not exfoliate well.

Exploratory Celiotomy

Excising the whole tumour if operable or taking a sample via shave biopsy or crush ligation allows histopathological confirmation.

Treatment

Surgery

Often at the time of diagnosis adenocarcinomas have already metastasised or local invasion has already taken place. If metastasis has no yet occurred surgical resection may be attempted with care to avoid iatrogenic trauma to the vascular supply to the proximal duodenum and obstruction of the main pancreatic duct. Total pancreatectomy and pancreaticoduodenectomy (Whipple's procedure) are not advised. Tumours of the body or base of the pancreas are inoperable. Gastrojejunostomy (gastrointestinal bypass) may be performed for short erm palliation. Small pancreatic adenomas may be removed via partial pancreatectomy.

Chemotherapy

Not recommended.

Radiotherapy

Not recommended.

Prognosis

Poor for adenocarcinomas on account of their invasiveness and early metastasis. Survival time is less than 1 year for such tumours.

References

Morris J, Dobson J (2001) Gastrointestinal Tract, in Small Animal Oncology, Blackwell Science, pp 140-142
Withrow S.J, Vail D.M (2007), Cancer of the Gastrointestinal Tract, in Withrow and MacEwen's Small Animal Clinical Oncology, fourth edition, Missouri, Saunders Elsevier, pp 479-480