MRI findings of intrahepatic cholangiocarcinoma with sarcomatoid differentiation: a retrospective case series

PURPOSE: To describe MRI findings of intrahepatic cholangiocarcinoma with sarcomatoid differentiation (s-iCCA), summarize associated clinical features, and explore imaging characteristics that may help distinguish it from conventional intrahepatic cholangiocarcinoma. MATERIALS AND METHODS: This retrospective single-center study reviewed surgically resected, pathology-proven s-iCCA between June 2018 and September 2025. Patients who underwent preoperative liver magnetic resonance imaging (MRI) with dynamic contrast enhancement and diffusion-weighted imaging (DWI) were included; tumors arising from the extrahepatic bile duct or gallbladder and those treated before MRI were excluded. Two radiologists evaluated lesion morphology, signal characteristics, enhancement pattern, and tumor spread independently. Clinical, laboratory, pathologic, treatment, and follow-up data were collected. RESULTS: Five patients (2 men, 3 women; mean age, 64 years) were included. Serum carbohydrate antigen 19-9 (CA 19-9) was elevated in all patients, whereas alpha-fetoprotein (AFP) and carcinoembryonic antigen (CEA) were within reference range in tested patients. All tumors presented as a dominant mass-forming lesion (3.4-9.4 cm; segments V-VII (right), n = 4; segments III/IV (left), n = 1). On MRI, lesions were hypointense on T1-weighted imaging and heterogeneously hyperintense on T2-weighted imaging; intratumoral hemorrhage suggested by T1 hyperintensity was observed in two patients, and extensive nonenhancing necrosis/cystic degeneration in three. All tumors showed marked diffusion restriction on DWI. Dynamic imaging demonstrated arterial peripheral rim enhancement with progressive and persistent heterogeneous enhancement without washout in all cases. Segmental bile duct dilatation was present in two patients, suspected portal vein tumor thrombus in one, and regional lymphadenopathy in three. Extensive necrosis or cystic degeneration was common and contributed to marked imaging heterogeneity. CONCLUSION: In this small series, s-iCCA frequently appeared as a necrotic and heterogeneous mass-forming lesion with diffusion restriction and progressive enhancement. Although these findings substantially overlap with those of conventional iCCA, prominent necrosis and marked heterogeneity may raise suspicion for sarcomatoid differentiation in the appropriate clinical context.