CA 19-9 is the most widely used serum marker for pancreatic adenocarcinoma. In which group of patients is this marker unreliable despite the presence of disease?

• A Patients with concurrent diabetes mellitus
• B Individuals who are Lewis antigen negative ✓
• C Patients with prior cholecystectomy
• D Individuals older than 70 years

Explanation

CA 19-9 is a sialylated Lewis blood group antigen produced by normal pancreatic and biliary epithelium. About 5 to 10 percent of the population, particularly in some ethnic groups, are Lewis antigen negative and cannot synthesize the antigen, so they never show elevated levels even with advanced pancreatic cancer. Diabetes, cholecystectomy, and age do not abolish antigen production, although benign biliary obstruction can falsely elevate it.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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