Malignant neoplasm of overlapping sites of biliary tract

This code signifies a primary malignant tumor that originates in and spans across two or more contiguous or overlapping sites within the biliary tract, where the point of origin cannot be clearly assigned to a single specific anatomical site. This includes cancers affecting structures like the intrahepatic and extrahepatic bile ducts, gallbladder, and ampulla of Vater simultaneously.

Use this code when documentation explicitly states a malignant neoplasm involving multiple, overlapping sites of the biliary tract, and the primary site cannot be localized to one specific part. This is often seen in advanced or diffuse biliary tract cancers. Supporting documentation would include pathology reports, operative notes, and imaging studies confirming the overlapping involvement.

• Do not use this code if the primary site can be clearly identified, even if there are metastases to other biliary tract structures.
• Distinguish from codes for specific biliary tract sites (e.g., gallbladder, common bile duct) when the tumor is confined to one.
• Always sequence this code as the primary diagnosis when it represents the main reason for the encounter.