A 55-year-old woman with primary sclerosing cholangitis (PSC) develops obstructive jaundice. CA 19-9 is 450 U/mL. MRI/MRCP shows a dominant stricture at the hilum with satellite lesions. Brushing cytology is reported as atypical. What is the most reliable diagnostic investigation to establish cholangiocarcinoma?

• A Endoscopic biopsy via ERCP
• B Serum IgG4 level
• C Percutaneous liver biopsy
• D Fluorescence in situ hybridization (FISH) on biliary brushings ✓

Explanation

Fluorescence in situ hybridization (FISH) on biliary brushings has a higher sensitivity than routine cytology for detecting chromosomal polysomy or specific chromosomal abnormalities in cholangiocarcinoma superimposed on PSC. Standard cytology has only 20–40% sensitivity in this setting; FISH improves this to approximately 60–70% without additional procedural risk. Serum IgG4 helps exclude IgG4-related sclerosing cholangitis (a mimic). Percutaneous biopsy carries seeding risk and is not preferred for potentially resectable hilar cholangiocarcinoma.

Reference: Bailey & Love's Short Practice of Surgery, 27th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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