Imaging of mass-forming intrahepatic cholangiocarcinoma: from detection to personalized treatments.

Mass-forming intrahepatic cholangiocarcinoma (MF-iCCA) represents the most frequent phenotype of intrahepatic CCA in Europe, yet its insidious clinical onset and tendency toward late presentation translate into a poor prognosis, with only 20-30% of patients eligible for curative resection. In this context, imaging plays a pivotal role, spanning from initial lesion detection and characterization to staging, treatment selection, and response assessment. Contrast-enhanced computed tomography (CT) and magnetic resonance imaging (MRI) constitute the backbone of diagnostic workup, with complementary strengths: CT offers superior spatial resolution for vascular assessment, while MRI, enhanced by diffusion-weighted imaging (DWI) and hepato-biliary phase sequences, provides higher sensitivity for intrahepatic staging and tumor delineation. Contrast-enhanced ultrasound (CEUS) serves as a valuable adjunct for differential diagnosis. Accurate resectability assessment requires careful evaluation of vascular involvement, future liver remnant (FLR) volume, and metastatic spread, with 18 F-FDG-PET playing an incremental role in nodal staging. In the era of personalized therapy, including chemo-immunotherapy, targeted agents, and locoregional treatments, functional response criteria beyond RECIST 1.1 are increasingly essential. A thorough knowledge of expected post-treatment imaging appearances is critical to avoid misclassification of treatment effects as disease progression. This narrative review aims to provide a comprehensive, imaging-focused overview of MF-iCCA, covering its radiological features and differential diagnosis, the role of imaging in staging and resectability assessment, imaging-based criteria guiding personalized treatment selection, and expected post-treatment imaging findings.