Which specific slide stain is used to confirm a hepatocellular origin of a tumor?

Immunohistochemical Staining for Hepatocellular Origin

To confirm hepatocellular origin of a tumor, use a panel of immunohistochemical markers including HepPar-1, Arginase-1, CD10, pCEA (polyclonal carcinoembryonic antigen), glypican-3, and BSEP, with CD10, pCEA, and BSEP showing superior specificity and sensitivity compared to HepPar-1 and glypican-3. 1

Recommended Immunohistochemical Panel

The 2025 EASL guidelines provide clear direction on confirming hepatocellular differentiation through immunohistochemistry. The optimal approach involves:

Primary Hepatocellular Markers (in order of performance):

• CD10 - highest performance marker
• pCEA (polyclonal CEA) - shows characteristic canalicular staining pattern unique to hepatocellular tumors 2
• BSEP - highest performance marker
• Arginase-1 - reliable hepatocellular marker
• HepPar-1 - traditional marker but lower specificity (stains 16/34 gastric carcinomas) 3
• Glypican-3 - lower performance than CD10/pCEA/BSEP

Key Staining Pattern to Recognize:

The canalicular staining pattern with polyclonal CEA is pathognomonic for hepatocellular carcinoma - this pattern is unique and not seen in other tumor types 2. This appears as delicate linear staining outlining bile canaliculi between hepatocytes, rather than diffuse cytoplasmic staining seen in adenocarcinomas.

Distinguishing from Cholangiocarcinoma

When differentiating hepatocellular from cholangiocellular origin 1:

Negative markers for HCC (positive in cholangiocarcinoma):

• Cytokeratin 7 (CK7) - should be negative
• Cytokeratin 19 (CK19) - should be negative

Positive markers for HCC:

• The hepatocellular panel listed above should be positive

Additional Helpful Stains

Reticulin Stain

While not immunohistochemical, reticulin stain is extremely useful for confirming HCC 1, 4, 5:

• Normal liver: reticulin framework outlines thin trabeculae (1-2 cells thick)
• HCC: shows reticulin loss, decreased staining, or widened trabeculae (>3 cells thick)
• Virtually absent or markedly decreased reticulin supports HCC diagnosis 5

Important caveat: Rare well-differentiated HCCs can show preserved reticulin networks surrounding individual tumor cells 4, so this should not be used as the sole criterion.

Practical Algorithm

1. Start with morphology - look for architectural features (unpaired arteries, sinusoidal capillarization, stromal invasion)

2. Apply hepatocellular marker panel:

   • First tier: CD10, pCEA, BSEP
   • Second tier: Arginase-1, HepPar-1, glypican-3

3. Look for canalicular pattern with pCEA - if present, this is diagnostic

4. Exclude cholangiocellular differentiation with CK7/CK19 (should be negative)

5. Add reticulin stain to assess architectural pattern

6. For malignancy confirmation in small lesions (<2 cm), consider the three-marker panel of glypican-3, glutamine synthetase, and heat shock protein 70 (100% specificity when all three positive) 1

Critical Pitfalls to Avoid

• Do not rely on single markers - HepPar-1 alone has significant false positives in gastric carcinomas 3
• Monoclonal CEA should be negative in HCC (positive in adenocarcinomas) 2
• EMA (epithelial membrane antigen) may be positive in 40% of HCCs, so don't use it to exclude HCC 2
• Cytokeratin AE1/AE3 is usually negative in HCC (15% positive), whereas most adenocarcinomas are strongly positive 2
• Reticulin patterns can vary - rare HCCs maintain reticulin framework 4

The combination of positive hepatocellular markers (especially canalicular pCEA pattern), negative cholangiocytic markers (CK7/CK19), and reticulin loss provides the most reliable confirmation of hepatocellular origin 1.