A 55-year-old woman with a history of primary sclerosing cholangitis (PSC) presents with progressive jaundice and weight loss. MRI shows a 3 cm hilar mass with biliary obstruction. Which serum marker is most useful (though not perfectly specific) for diagnosis of cholangiocarcinoma in this context?
- A AFP (alpha-fetoprotein)
- B CEA (carcinoembryonic antigen)
- C CA 19-9 (carbohydrate antigen 19-9) ✓
- D CA 125
Correct answer: C. CA 19-9 (carbohydrate antigen 19-9)
Explanation
CA 19-9 is the most clinically useful serum marker for cholangiocarcinoma, with sensitivity ~60–70% and specificity ~80–90% in the appropriate clinical setting. It is particularly useful in patients with PSC where development of cholangiocarcinoma is a major risk. However, CA 19-9 can be falsely elevated in cholestasis/benign biliary obstruction and is not produced by individuals who are Lewis antigen-negative (~5–10%). AFP is the marker for HCC; CEA is less sensitive for cholangiocarcinoma; CA 125 is associated with ovarian and peritoneal malignancies.
Reference: Bailey & Love's Short Practice of Surgery, 27th ed.
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