HMGB1 levels correlated strongly with tumor burden and aggressiveness: values rose in parallel with increasing tumor diameter (r = 0.874, p < 0.001) and were highest in sarcomatoid variants—whose median HMGB1 exceeded 499 pg/mL—underscoring its association with high-grade histology (p = 0.035 for subtype differences; p = 0.002 for diameter comparisons). Here, HMGB1 is linked to neoplasm.