Exocrine pancreatic neoplasia

Pancreatic adenomas are benign tumours, which are usually singular and can be differentiated from pancreatic nodular hyperplasia by the presence of a capsule. Pancreatic adenocarcinoma is the most common neoplastic condition of the exocrine pancreas in the dog and cat, but occurs infrequently. Adenocarcinomas usually originate from the duct system but can also originate from acinar tissue. A few cases of pancreatic sarcomas, i.e. spindle cell sarcoma and lymphosarcoma, have been reported. Whether these tumours are primary neoplastic lesions of the exocrine pancreas, metastatic lesions from tumours of other organs or a localized lesion of a multicentric neoplasia is open to question.

Aetiology and pathophysiology

The aetiology of neoplastic conditions of the exocrine pancreas is unknown. Benign neoplastic lesions can lead to displacement of cranial abdominal organs. However, these changes are subclinical in most cases and the diagnosis is often made as an incidental finding at necropsy examination. In very few cases a benign growth can obstruct the pancreatic duct and cause secondary atrophy of the remaining exocrine pancreas, leading to EPI. Adenocarcinomas can also cause displacement of cranial abdominal organs and obstruction of the pancreatic duct. In addition, adenocarcinomas can be associated with tumour necrosis and resulting pancreatic inflammation when the tumour outgrows its vascular supply. Pancreatic adenocarcinomas can also spread to neighbouring or distant organs.

Exocrine pancreatic neoplasia: Diagnosis

Clinical signs: The presentation of patients with exocrine pancreatic neoplasia is non-specific and clinical signs observed are often those of chronic pancreatitis, including vomiting, anorexia, diarrhoea or chronic weight loss. Multifocal necrotizing steatitis has been described in a few dogs that were ultimately diagnosed with pancreatic adenocarcinoma. Clinical signs related to metastatic lesions (e.g. lameness, bone pain, dyspnoea) have also been reported in some cases of pancreatic adenocarcinoma. Recently several cases of paraneoplastic alopecia have been reported in cats with pancreatic adenocarcinoma. The reported alopecia consisted of generalized alopecia of the ventrum, limbs and face in most cases, and diffuse zones of alopecia in the remaining cats ().

Diagnostic imaging: Radiography findings are also non-specific in most cases. Abnormal findings include: decreased contrast in the cranial abdomen, suggesting peritoneal effusion into this area; transposition of the spleen caudally; and shadowing in the pyloric region. In some cases abdominal radiography can suggest the presence of a mass in the cranial abdomen. In most cases a soft tissue mass can be identified by abdominal ultrasonography in the region of the pancreas. However, in many if not most cases, pancreatic origin of the mass can not be conclusively established. Similarly, neoplastic lesions of neigh bouring organs may be falsely presumed to be of pancreatic origin. Also, patients with severe pancreatitis may show, on ultrasound examination, a mass effect in the area of the pancreas that can be confused with a pancreatic adenocarcinoma. If peritoneal effusion is identified on abdominal ultrasonography, a sample should be aspirated and evaluated cytologically, although neoplastic cells are not routinely identified on cytology as they do not readily exfoliate. Fine needle aspiration or transcutaneous biopsy under ultrasound guidance can be attempted when suspicious masses are identified, and has been reposed to be successful in approximately 25% of all cases. The low success rate of fine needle aspiration is probably due to the lack of exfoliation of pancreatic adenocarcinoma cells. In other cases carcinoma cells can be identified but the origin of the cells cannot be determined conclusively. Ultrasound-guided biopsy with histopathological evaluation of biopsy specimens has been reported inffequently but in one study ultrasoundguided biopsy of a pancreatic mass resulted in a diagnosis of pancreatic adenocarcinoma in both of two cases. In two of three more cases biopsy of the liver revealed metastatic carcinoma. I n many cases the diagnosis is made at exploratory laparotomy or even on necropsy examination.

Laboratory rests: Neutrophilia, anaemia, hypokalaemia, bilirubinaemia, azotaemia, hyperglycaemia and elevations of hepatic enzymes have all been reported in affected patients, but results of routine blood tests may be unremarkable. Elevations of hepatic enzymes and serum bilirubin concentration are identified most commonly. Hyperglycaemia, when present, is related to concurrent destruction of pancreatic beta cells. Some dogs with pancreatic adenocarcinoma have extremely high serum lipase activities that reach as much as 25 times the upper limit of the reference range. A single dog with a pancreatic adenocarcinoma and pseudohyperparathyroidism, leading to hypercalcaemia has been described in the literature.

Treatment and prognosis

Pancreatic adenomas are benign and theoretically do not need to be treated, unless they cause clinical signs. However, since 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 in these cases is excellent.

Pancreatic adenocarcinomas often present at a late stage of the disease; metastatic disease is usually present at the time of diagnosis. The most common sites of metastatic disease are the liver, abdominal and thoracic lymph nodes, mesentery, intestines and the lungs, but various other sites have also been reported. In those few cases when gross metastatic lesions are not identified at the time of diagnosis, surgical resection of the tumour may be attempted, but owners should be forewarned that clean surgical margins are only rarely achieved. Total pancreatectomy and pancreaticoduodenectomy, though theoretically possible, have not been described in dogs or cats with spontaneous disease. Extrapolation from human patients suggests high morbidity and mortality for these procedures. Chemotherapy and radiation therapies have shown little success in human or veterinary patients with pancreatic adenocarcinomas. Overall, the prognosis for dogs and cals with pancreatic adenocarcinoma is grave.