Why the liver is unique organ ? explained by Dr Vineet Gautam, Liver transplant surgeon

All liver functions remain normal even if 70% of it is removed (provided the remaining 30% is healthy). Thats why more than half the liver can be removed from the donor for transplantation purposes, without causing any derangement of liver function or any other serious harm to the donor. In persons with cancer of the liver, large portions of cancerous liver can be removed without causing harm or compromise to liver function.
The liver is the only organ in the body which can regenerate itself after large portions of it are removed. Small remnants of liver grow back to normal size within a few weeks to few months. Thats why it is safe to remove large portions of liver from living donors and persons with liver cancer or liver tumor.
This is also why half livers transplanted into liver failure patients are very successful since they soon grow to normal size.