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.