Acinar cell carcinoma of exocrine pancreas in two horses.

This research article describes two cases of pancreatic acinar cell carcinoma, a type of pancreatic cancer, in horses. The horses had shown general signs of illness for a few weeks and, due to the seriousness of the disease, had to be euthanized. Postmortem examinations revealed multiple tumors in various organs, including the pancreas, liver, and lungs.

Disease Presentation and Examination

• The study involves two horses that presented with unspecified symptoms over a few weeks, leading veterinarians to euthanize them due to a grim prognosis.
• During an autopsy (or necropsy in animals), they discovered multiple small white nodules, replacing pancreatic tissue in both horses. The nodules also spread to the serosal surface of the abdominal cavity, liver, and lungs.

Microscopic Findings

• Upon microscopic examination, the malignant cells from these nodules were arranged in acini, which are tiny, saclike formations present in various organs. They contained numerous zymogen granules in the first horse and fewer in the second. Zymogen granules store enzymes inactive form.
• Special antibody-staining tests (immunohistochemistry) showed that these tumor cells expressed amylase (a digestive enzyme) and pan-cytokeratin (a protein found in epithelial cells).
• Importantly, these cancerous cells didn’t produce insulin or neuron-specific enolase, ruling out certain types of pancreatic and nerve cell tumors.
• In horse number 2, a minor portion of the neoplastic cells expressed glucagon (a hormone regulating blood sugar levels) and synaptophysin (a protein in nervous tissue), although they were confirmed to be cancerous.

Electron Microscopic Analysis

• The presence of zymogen granules was further confirmed using electron microscopy. In addition, they noticed rare fibrillary or glucagon granules in the first and second horses, respectively.

Final Diagnosis

• The final diagnosis for both horses was pancreatic acinar cell carcinoma, a rare type of pancreatic cancer. This was based on the unique microscopic and biochemical characteristics of these cancers.