The lymph nodes are interconnected and eventually return the purified serum to the bloodstream. Moreover, the bile duct area, and digestive system in general, has a rich blood supply from both major arteries and draining veins. The cells in the bile duct system grow rapidly in womb life, childhood and through puberty. In adulthood, they divide much more slowly, to replace those that die of injury or old age. Like all cell division in the body, this process is tightly controlled to proceed in an orderly manner.
Biliary cancer starts within a single cell.
Something changes the control mechanisms within this cell, the genes become damaged, and it starts dividing in a rapid and disorganized manner . A tumor is merely a swelling, as isn't necessarily cancerous. By contrast, a malignant tumor is cancer and has a capacity to spread to any area of the body. Thus, any metastatic tumor is by definition cancerous. About 3000 of the cases are in the liver itself, the remaining 17,000 cases are in the Gall Bladder and bile drainage ducts.