Final answer:
The hepatic portal vein is the main route by which pancreatic cancer can spread to the liver, as it directly carries blood from the pancreas and other organs of the digestive system to the liver for processing.
Step-by-step explanation:
The route by which pancreatic cancer can easily spread to the liver is through the hepatic portal vein. The hepatic portal system is a critical nexus between the digestive system and liver, where absorbed nutrients, as well as waste materials from the spleen and digestive tract, are processed. This system begins and ends in capillaries, starting in the capillaries of the stomach, small intestine, large intestine, and spleen, continuing through the hepatic portal vein, and ending in the specialized capillaries within the liver, the hepatic sinusoids.
Considering the connections within the hepatic portal system, the hepatic portal vein is the main vessel for carrying materials from the spleen, pancreas, and gastrointestinal tract directly to the liver. As pancreatic cancer cells enter the bloodstream, they can easily be carried by the portal circulation right into the liver, thus making the hepatic portal vein the most likely route for metastasis from the pancreas to the liver.