As far as tumors of the liver are concerned they range in variety from SIMPLE BENIGN tumors to AGRRESSIVE MALIGNANT ones.....Keeping in view your scenario that tumor has involved the bile duct it seems to be an AGGRESSIVE lesion BUT again thorough testing is requred in order to get the right diagnosis. Some differntials are as : 1:If your dad has got underlying CHRONIC LIVER DISEASE CIRRHOSIS due to any etiology like AlcohoL , HBV , HCV , AUTOUMMUNE HEPATITIS , METABOLLIC DISEASE LIKE HEMACHROMATOSIS then most probable tumor is HEPATOCELLULAR CARCINOMA which requires SERUM AFP levels liver dynamic scan for its diagnosis... 2: Second is CHOLANGIOCARCINOMA its a tumor of the bile ducts mostly presents with the obstructive jaundice clay colour stools and dark urine and itching all over the body with wt. loss CA-9 is used as serum marker for diagnosis along with CT oR MRI. 3: other probability is METASTATIC liver tumors which means primary tumor is somwhere else in body like in COLON and has secondaries in liver..PET scan is used for diagnosis .... Hope u get ur answer if u have any querries feel free to ask... regards