Can contrast enhanced ultrasound differentiate intrahepatic cholangiocarcinoma from hepatocellular carcinoma

BACKGROUND Hepatocellular carcinoma (HCC) and intrahepatic cholangiocarcinoma (ICC) differ in treatment and prognosis, warranting an effective differential diagnosis between them. The LR-M category in the contrast-enhanced ultrasound (CEUS) liver imaging reporting and data system (LI-RADS) was set up for lesions that are malignant but not specific to HCC. However, a substantial number of HCC cases in this category elevated the diagnostic challenge. AIM To investigate the possibility and efficacy of differentiating ICC from HCC classified in the LR-M category according to the CEUS LI-RADS. METHODS Patients with complete CEUS records together with pathologically confirmed ICC and LR-M HCC (HCC classified in the CEUS LI-RADS LR-M category) between January 2015 and October 2018 were included in this retrospective study. Each ICC was assigned a category as per the CEUS LI-RADS. The enhancement pattern, washout timing, and washout degree between the ICC and LR-M HCC were compared using the χ2 test. Logistic regression analysis was used for prediction of ICC. Receiver operating characteristic (ROC) curve analysis was used to investigate the possibility of LR-M criteria and serum tumor markers in differentiating ICC from LR-M HCC. RESULTS A total of 228 nodules (99 ICCs and 129 LR-M HCCs) in 228 patients were included. The mean sizes of ICC and LR-M HCC were 6.3 ± 2.8 cm and 5.5 ± 3.5 cm, respectively (P = 0.03). Peripheral rim-like arterial phase hyperenhancement (APHE) was detected in 50.5% (50/99) of ICCs vs 16.3% (21/129) of LR-M HCCs (P 0.05). Marked washout was observed in 23.2% (23/99) of ICCs and 7.8% (10/129) of LR-M HCCs (P = 0.002), while this feature did not show up alone either in ICC or LR-M HCC. Homogeneous hyperenhancement was detected in 15.2% (15/99) of ICCs and 37.2% (48/129) of LR-M HCCs (P < 0.001). The logistic regression showed that rim APHE, carbohydrate antigen 19-9 (CA 19-9), and alpha fetoprotein (AFP) had significant correlations with ICC (r = 1.251, 3.074, and -2.767, respectively; P < 0.01). Rim APHE presented the best enhancement pattern for diagnosing ICC, with an area under the ROC curve (AUC) of 0.70, sensitivity of 70.4%, and specificity of 68.8%. When rim hyperenhancement was coupled with elevated CA 19-9 and normal AFP, the AUC and sensitivity improved to 0.82 and 100%, respectively, with specificity decreasing to 63.9%. CONCLUSION Rim APHE is a key predictor for differentiating ICC from LR-M HCC. Rim APHE plus elevated CA 19-9 and normal AFP is a strong predictor of ICC rather than LR-M HCC. Early washout and marked washout have limited value for the differentiation between the two entities.