Biliary Tract Cancer: A New Invasion-Depth Classification : Annals of Surgery | October 2026

What Did the Study Find?

This study evaluated 191 patients with biliary tract cancers involving the cystic duct junction, proposing a unified depth-based T classification for junctional cholangiocarcinoma (JCC).

• 46% of tumours (88/191) could not be reliably classified as perihilar cholangiocarcinoma (PCC), distal cholangiocarcinoma (DCC), or cystic duct carcinoma (CDC) using anatomical predominance.
• Five-year survival varied considerably by anatomical classification: 70% for DCC, 48% for unclassifiable tumours, 36% for PCC and 29% for CDC.
• Investigators proposed a unified T classification based on histological depth of invasion:
• T1: ≤1 mm
• T2: >1–5 mm
• T3: >5–10 mm
• T4: >10 mm
• In the 88 unclassifiable tumours, five-year survival was 83%, 67%, 44% and 0% across T1–T4, respectively.
• Across all 191 junctional cancers, five-year survival was 88%, 60%, 41% and 24%, respectively.
• Depth-based staging showed better prognostic discrimination in unclassifiable tumours (C-index 0.654) than the existing site-specific classifications (0.563–0.613).

Why Does It Matter?

Tumours arising near the cystic duct junction frequently cross conventional anatomical boundaries, making their classification difficult and potentially inconsistent.

A shared invasion-depth system could improve pathological staging, prognostic counselling and comparability of surgical oncology outcomes across institutions.

GastroAGI Takeaway

For biliary cancers around the cystic duct junction, depth of invasion may predict survival more consistently than anatomical origin alone.

Nearly half of these tumours were anatomically unclassifiable, yet the proposed depth-based T system provided meaningful survival stratification.

This supports considering junctional cholangiocarcinoma as a distinct anatomical grouping with a potentially unified staging framework.

Important limitation: This was a retrospective study of 191 patients, and the improvement in prognostic discrimination was modest. External multicentre validation is required before replacing established AJCC staging systems.