Contrast-enhanced ultrasound for diagnosing subtypes of intrahepatic cholangiocarcinoma: a comparative study with poorly differentiated hepatocellular carcinoma.

[BACKGROUND] Pathologically, intrahepatic cholangiocarcinoma (ICC) is classified into small-duct (SD) type and large-duct (LD) type, each with distinct clinicopathological characteristics. The contrast-enhanced ultrasound (CEUS) features of the two ICC types remain insufficiently explored.

[PURPOSE] To evaluate liver CEUS imaging for differentiating the SD and LD types of ICC and further compare them with poorly differentiated hepatocellular carcinoma (pHCC).

[MATERIALS AND METHODS] A single-center retrospective study enrolled 252 patients with SD-type ICC, LD-type ICC, or pHCC between October 2017 and August 2023. Logistic regression analyses identified independent clinical, pathological, ultrasound, and CEUS predictors. Based on these features, a decision tree-based diagnostic model was developed. The model's performance was evaluated using receiver operating characteristic (ROC) curve analysis in both the training and validation cohorts, as well as in subgroup stratified by tumor size ≤ 5 cm and > 5 cm. Differences in overall survival (OS) and recurrence-free survival (RFS) based on the model were further analyzed.

[RESULTS] Overall, 252 patients (mean age, 58.4 ± 10.7 years; 174 males) with 140 SD-type ICC, 55 LD-type ICC and 57 pHCC were enrolled. Multivariate analysis revealed that AFP, CEA, CA19-9, HBsAg status, arterial phase enhancement pattern, washout time ≤ 45 s, and marked washout were independent predictors for tumor categories differentiation (all P <.05). The decision tree-based model incorporating the major features demonstrated excellent performance in both the training cohort (AUC 0.89) and validation cohort (AUC 0.88), as well as in tumor size ≤ 5 cm (AUC 0.90) and > 5 cm (AUC 0.84). OS was significantly worse in LD-type ICC patients compared to SD-type and pHCC (P <.05 for both), while RFS showed no significant difference.

[CONCLUSIONS] A user-friendly, decision tree-based diagnostic model was developed to accurately predict ICC subtypes and pHCC, facilitating improved clinical decision-making. The decision tree-based diagnostic model effectively diagnosed small-duct type and large-duct type intrahepatic cholangiocarcinoma, as well as poorly differentiated hepatocellular carcinoma.