A 45-year-old woman with primary sclerosing cholangitis (PSC) undergoes surveillance colonoscopy and is found to have high-grade dysplasia in flat mucosa of the right colon. Her serum CA19-9 is markedly elevated. The most important next diagnostic consideration is:

• A Pancreatic adenocarcinoma as the primary source of CA19-9 elevation unrelated to PSC
• B Cholangiocarcinoma (CCA) arising within the biliary strictures of PSC, as CA19-9 elevation in this context should prompt biliary brushings/biopsy and MRCP/PET-CT for CCA ✓
• C Hepatocellular carcinoma complicating PSC-related cirrhosis, for which CA19-9 is the primary tumor marker
• D Colorectal carcinoma as the source of elevated CA19-9 given the colonoscopic findings of high-grade dysplasia

Explanation

PSC carries a 10–15% lifetime risk of cholangiocarcinoma (CCA), which is a major cause of mortality in PSC patients and can be difficult to distinguish from dominant biliary strictures by imaging alone. CA19-9 is elevated in biliary tract malignancies; a level >130 U/mL in PSC has reported sensitivity ~79% and specificity ~98% for CCA. The combination of elevated CA19-9, worsening biliary strictures, and weight loss in a PSC patient mandates urgent CCA evaluation via MRCP, endoscopic biliary brush cytology with FISH, and PET-CT. While CA19-9 is also elevated in pancreatic cancer, the primary concern in PSC context is CCA. CA19-9 is not the marker for HCC (AFP is). CRC rarely causes significant CA19-9 elevation without mucinous histology or liver metastases.

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

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Written and medically reviewed by the StethoPrep medical team.