A Grading System of Intratumoral Tertiary Lymphoid Structure for Combined Hepatocellular-Cholangiocarcinoma: A Multicenter Pathological Study.

Purpose: Tertiary lymphoid structure (TLS) has been well-established across multiple tumor types for predicting efficacy of immunotherapy and prognostic evaluation. However, its role in combined hepatocellular-cholangiocarcinoma (cHCC-CCA) remains unclear. Refinement of TLS pathological assessment could potentially optimize postoperative management in these patients. This study aimed to develop a practical histopathological grading system of intratumoral TLS to improve prognostic stratification of cHCC-CCA patients. Patients and Methods: A cohort of 310 cHCC-CCA patients undergoing hepatectomy with curative intent was analyzed. Three pathologists re-evaluated pathological slides to establish a four-tier TLS grading system: TLS 0 (absent), TLS 1 (immature TLS only), TLS 2a [single mature TLS (mTLS)], and TLS 2b (multiple mTLS). Associations with recurrence-free survival (RFS), overall survival (OS), early RFS (≤1 year), late RFS (>1 year), and recurrence patterns were assessed. Predictive factors for TLS were also investigated. Results: Patients were stratified into TLS 0 (29.4%), TLS 1 (51.6%), TLS 2a (6.8%), and TLS 2b (12.3%). Survival outcomes significantly correlated with TLS presence and maturation. Median RFS increased stepwise: 0.24 years (TLS 0), 0.49 years (TLS 1), 1.13 years (TLS 2a), and 1.16 years (TLS 2b) (P<0.001). Median OS also improved progressively: 1.32 years (TLS 0), 2.20 years (TLS 1), 3.24 years (TLS 2a), and 10.04 years (TLS 2b) (P<0.001). TLS presence was associated with increased extrahepatic recurrence. The TLS grading system emerged as an independent prognostic factor for RFS, OS, and early RFS. Smaller tumor diameter was the sole significant predictive factor for both TLS and mTLS. Conclusion: This novel TLS grading system effectively stratifies prognosis in cHCC-CCA, with increasing intratumoral mTLS indicating better outcomes. This practical method can be integrated into routine pathological reporting to aid clinical decision-making.