Gastric adenocarcinoma in a horse with portal vein metastasis and thrombosis: a novel cause of hepatic encephalopathy.

The research article discusses a unique case where a 17-year-old horse suffered from hepatic encephalopathy caused by gastric adenocarcinoma that metastasized to its liver and portal vein.

Case Overview

• The horse, a 17-year-old Quarter horse mare was referred to Cornell University for a thorough postmortem examination after it exhibited signs of encephalopathy which included depression, mania, and blindness for over 72 hours.
• A plasma sample and analysis of the horse’s cerebral spinal fluid revealed hyperammonemia, indicating that the horse was likely suffering from hepatic encephalopathy.

Gross Necropsy Examination Findings

• The autopsy on the deceased horse revealed mild icterus (jaundice), a transmural mass in the glandular portion of the gastric fundus (the upper part of the stomach where the esophagus enters the stomach), multiple clusters of abnormal tissue (masses) prevalent throughout the liver, and a large tumor thrombus (blood clot) in the portal vein (blood vessel that carries blood from gastrointestinal tract and spleen to the liver).

Microscopic Examination Findings

• Under the microscope, similar neoplastic epithelial cells were found in the gastric mass, hepatic masses as well as the portal vein thrombus. This indicates that these cells likely originated from the same origin, resulting in the formation of the masses in different parts of the body.
• The neoplastic cells were seen to form variably sized acini (small ball-shaped arrangement of cells) and branching cords separated by a dense desmoplastic stromal tissue, further confirming the cancerous nature of the cells.
• There were numerous Alzheimer type II astrocytes seen throughout the cerebral frontal cortex, a unique feature of hepatic encephalopathy.

Hepatic Encephalopathy

• The hepatic encephalopathy in the horse was caused by gastric adenocarcinoma, a type of stomach cancer, which metastasized (spread) to the liver and the portal vein of the horse, a novel finding documented in this case.
• The research further discusses the clinical and pathological lesions from this case, as well as elaborating on the role of hyperammonemia (high levels of ammonia in the blood, a condition often found in liver disease) and portal vein thrombosis (blood clot in the portal vein) in the pathogenesis (development) of hepatic encephalopathy.