Exocrine pancreatic neoplasia is rare in dogs and cats. Clinical signs are nonspecific, leading to a late diagnosis in most cases. Diagnosis is primarily by ultrasonographic or radiographic examination, with confirmation by cytological or histological examination. Surgical excision can be attempted but is typically unsuccessful.
Neoplasia of the exocrine pancreas is quite rare in dogs and cats.
Exocrine pancreatic neoplasia is distinct from endocrine pancreatic neoplasia, types of which include insulinomas, gastrinomas, and glucagonomas.
Etiology and Pathophysiology of Exocrine Pancreatic Neoplasia in Dogs and Cats
Exocrine pancreatic neoplasia arises from uncontrolled proliferation of cells of the exocrine pancreas (acinar and duct tissue) and can be classified as benign (pancreatic adenoma) or malignant (pancreatic adenocarcinoma).
Pancreatic adenomas are benign tumors that are usually singular and can be differentiated from pancreatic nodular hyperplasia by the presence of a capsule.
Pancreatic adenocarcinoma is the most common primary neoplastic condition of the exocrine pancreas in dogs and cats but is rare overall in both species.
Pathogenesis of Exocrine Pancreatic Neoplasia
Benign neoplasms of the exocrine pancreas can lead to transposition of organs of the cranial abdominal cavity. However, these changes are subclinical in most cases, and the diagnosis is often made as an incidental finding during necropsy. In rare cases, the neoplastic growth can obstruct the pancreatic duct and cause secondary atrophy of the remaining exocrine pancreas, leading to exocrine pancreatic insufficiency.
Adenocarcinomas may lead to tumor necrosis if the tumor outgrows its blood supply. Tumor necrosis causes local inflammation, which can lead to clinical signs of pancreatitis.
Malignant neoplasms may also spread to neighboring or distant organs.
Clinical Findings of Exocrine Pancreatic Neoplasia in Dogs and Cats
Clinical signs of dogs and cats with exocrine pancreatic neoplasia are nonspecific, and many cases remain subclinical until late in the disease process.
Some animals show clinical signs suggestive of pancreatitis. Jaundice may occur if bile duct obstruction develops.
Clinical signs related to metastatic lesions (eg, lameness, bone pain, dyspnea) have also been reported in some cases of pancreatic adenocarcinoma.
Progressive, bilaterally symmetrical alopecia affecting the ventrum and limbs has been reported as a paraneoplastic syndrome in cats with pancreatic adenocarcinoma.
Diagnosis of Exocrine Pancreatic Neoplasia in Dogs and Cats
Diagnostic imaging
Cytological or histological examination
CBC, biochemical profile, and measurement of pancreatic markers (eg, serum lipase activity, serum pancreatic lipase immunoreactivity concentration) are all nonspecific in dogs and cats with exocrine pancreatic neoplasia.
Radiographic findings are also nonspecific in most cases.
Abdominal ultrasonography generally shows a soft tissue mass near the pancreas; however, in many cases, continuation of the mass with pancreatic tissue cannot be conclusively demonstrated. Also, neoplastic lesions of neighboring organs may be falsely presumed to be of pancreatic origin. Abdominal ultrasonography of animals with pancreatitis may show a mass effect in the pancreatic area that must not be confused with pancreatic neoplasia.
Pearls & Pitfalls
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Abdominal CT and MRI have not been systematically evaluated in dogs and cats with pancreatic neoplasia but may be superior in tumor localization compared to other imaging modalities.
If peritoneal effusion is present, a sample should be aspirated and evaluated cytologically. However, in most cases neoplastic cells do not readily exfoliate into the peritoneal effusion, and neoplastic cells are not identified on cytological examination.
Fine-needle aspiration or transcutaneous biopsy under ultrasonographic guidance can be attempted when suspicious masses are identified.
In many cases, the diagnosis is made at exploratory laparotomy or necropsy.
Treatment and Prognosis of Exocrine Pancreatic Neoplasia in Dogs and Cats
Typically unsuccessful, with a poor prognosis
Pancreatic adenomas are benign and generally do not require therapy unless they cause clinical signs due to the effects of an intra-abdominal space-occupying lesion. However, because the final diagnosis of pancreatic adenocarcinoma is often made at exploratory laparotomy, a partial pancreatectomy should be performed even in cases of suspected pancreatic adenoma. The prognosis for dogs and cats with pancreatic adenoma is considered excellent.
Pancreatic adenocarcinomas are often diagnosed at a late stage of the disease, and metastatic disease at the time of diagnosis is quite common in both dogs and cats. Common sites for metastasis are the liver, abdominal and thoracic lymph nodes, mesentery, intestines, and lungs, but other metastatic sites have also been reported (1). In those few cases when gross metastatic lesions are not identified at the time of diagnosis, surgical tumor resection may be attempted; however, clean surgical margins are rarely achieved, and owners should be forewarned.
Neither chemotherapy nor radiation therapy has shown much success in human or veterinary patients with pancreatic adenocarcinomas. The prognosis for dogs and cats with pancreatic adenocarcinoma is considered grave. A single case report of a cat with pancreatic adenocarcinoma detailed successful management with surgical resection and toceranib phosphate (2.78 mg/kg, PO, every 48 hours) with a reported progression-free interval of 1,148 days (2). However, further studies are needed.
Key Points
Most exocrine pancreatic malignant neoplasms are diagnosed late in the disease process.
A diagnosis of exocrine pancreatic neoplasia can only be confirmed by cytological or histological examination.
Treatment of dogs or cats with a pancreatic adenocarcinoma is largely unsuccessful.
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References
Linderman MJ, Brodsky EM, de Lorimier LP, Clifford CA, Post GS. Feline exocrine pancreatic carcinoma: a retrospective study of 34 cases. Vet Comp Oncol. 2013;11(3):208-218. doi:10.1111/j.1476-5829.2012.00320.x
Todd JE, Nguyen SM. Long-term survival in a cat with pancreatic adenocarcinoma treated with surgical resection and toceranib phosphate. JFMS Open Rep. 2020;6(1):2055116920924911. doi:10.1177/2055116920924911
