ERG Immunohistochemistry as an Endothelial Marker for Assessing Lymphovascular Invasion.

BACKGROUND

ERG, a member of the ETS family of transcription factors, is a highly specific endothelial marker. We investigated whether the use of ERG immunostaining can help pathologists detect lymphovascular invasion (LVI) and decrease interobserver variability in LVI diagnosis.

METHODS

Fifteen cases of surgically resected colorectal cancers with hepatic metastasis were selected and the most representative sections for LVI detection were immunostained with ERG, CD31, and D2-40. Eight pathologists independently evaluated LVI status on hematoxylin and eosin (H&E) and the corresponding immunostained sections and then convened for a consensus meeting. The results were analyzed by kappa (κ) statistics.

RESULTS

The average rate of LVI positivity was observed in 43% with H&E only, 10% with CD31, 29% with D2-40, and 16% with ERG. Agreement among pathologists was fair for H&E only (κ=0.27), D2-40 (κ=0.21), ERG (κ=0.23), and was moderate for CD31 (κ=0.55). Consensus revealed that ERG nuclear immunoreactivity showed better visual contrast of LVI detection than the other staining, with improved agreement and LVI detection rate (κ=0.65, LVI positivity rate 80%).

CONCLUSIONS

The present study demonstrated a superiority with ERG immunostaining and indicated that ERG is a promising panendothelial marker that might help pathologists increase LVI detection and decrease interobserver variability in LVI diagnosis.