Association between ultrasound-based biliary and parenchymal intrahepatic mass-forming cholangiocarcinoma subtypes and clinicopathological features and survival

Abstract Objective Mass-forming intrahepatic cholangiocarcinomas (MF-ICCs) can be classified into ductal and parenchymal types using magnetic resonance imaging (MRI). We aimed to subclassify MF-ICC into biliary and parenchymal types based on ultrasound (US) findings and to investigate the differences in their contrast-enhanced ultrasound (CEUS) patterns, clinicopathologic features, and prognosis. Methods In this study, 141 patients who underwent US with pathologically proven MF-ICC from two hospitals were retrospectively enrolled. MF-ICCs were divided into biliary (bMF-ICCs) and parenchymal MF-ICC (pMF-ICCs) based on the signs of bile duct dilation in US images. Clinicopathological, imaging, and short-term survival data were collected from medical records and compared. Results Among 141 patients (61.96 ± 10.15 years, 83 men), bMF-ICCs (33/141, 23.4%) showed significantly more CEA ≥ 5 µg/L (42.4% vs 20.2%, p = 0.01), microvascular invasion (54.5% vs 10.2%, p < 0.001), lymph node metastasis (48.5% vs 5.6%, p < 0.001), bile duct invasion (48.5% vs 5.6%, p < 0.001), and high Ki-67 expression (63.6% vs 38.9%, p = 0.01) than pMF-ICCs. Pathologically, bMF-ICCs were more inclined toward the large duct type (78.1% vs 11.7%, p < 0.001). In addition, the bMF-ICCs were usually located in the left lobe of the liver (63.6% vs 41.7%, p = 0.03). pMF-ICCs showed better overall survival than bMF-ICCs ( p = 0.04). Conclusions Subclassification of MF-ICCs into biliary and parenchymal types based on US is useful for discriminating clinicopathological characteristics. Critical relevance statement The subclassification of mass-forming intrahepatic cholangiocarcinoma (MF-ICC) into biliary (bMF-ICC) and parenchymal (pMF-ICC) subtypes using ultrasound can provide clinicopathological and prognostic information before surgery. Key Points We subclassified mass-forming intrahepatic cholangiocarcinomas into biliary and parenchymal types using ultrasound. Biliary and parenchymal types have different clinicopathological features and postsurgical outcomes. Biliary type above and below 50 mm exhibits different unfavorable clinicopathological characteristics. Our classification has certain similarities with MRI classification in clinicopathological characteristics. Graphical Abstract