Gross type of hepatocellular carcinoma reflects the tumor hypoxia, fibrosis, and stemness-related marker expression

Background: Hepatocellular carcinoma (HCC) is subclassified into five gross types, namely, vaguely nodular (VN), single nodular (SN), single nodular with extranodular growth (SNEG), confluent multinodular (CM), and infiltrative (INF) type. However, the pathological background underlying differences in biological behavior of different gross types of HCC remains unclear.

Methods: The histopathological features, clinical outcomes of HCC gross types, and their relationships with stemness-related marker status and fibrotic/hypoxic tumor microenvironment (TME) were evaluated in 266 resected HCCs. The stemness-related markers (CD24, CD44, CD133, SALL4, YAP1, K19 and EpCAM), fibrous tumor stroma (αSMA), and hypoxia (CAIX) were evaluated with immunohistochemistry.

Results: Poorer differentiation, reduced capsule formation, higher microvascular invasion, larger tumor size and larger area of necrosis were observed in order of VN-SN-SNEG-CM-INF type (p = 0.005 for all, linear-by-linear association). The expression of summed stemness-related markers and hypoxic/fibrotic TME showed an increasing trend in order of VN-SN-SNEG-CM-INF type (p < 0.005), and their expression well correlated with each other. INF type was found only in HCCs with hypoxic/fibrotic TME or high expression of stemness-related markers. CAIX expression and tumor necrosis ≥ 30% were independent prognostic markers for disease-specific survival. Early recurrence-free survival showed a significant difference based on gross types, revealing best outcome with VN type and worst outcome with INF type.

Conclusion: The marker expression of stemness-related and hypoxic/fibrotic TME of HCC showed an increasing trend in order of VN-SN-SNEG-CM-INF gross types, and their cross-talk may be involved in the determination of various gross-morphological features and their distinct biological behavior.