Intrahepatic cholangiocarcinoma (ICC) is a primary liver malignancy originating from intrahepatic bile duct epithelium. It is the second most common primary malignant tumor of the liver (10-15%). Unlike HCC, it rarely develops in the setting of cirrhosis. Desmoplastic (fibrous) stroma content determines ICC's imaging characteristics: peripheral arterial enhancement and progressive centripetal filling (delayed contrast accumulation in fibrous stroma). Capsular retraction and proximal bile duct dilatation are important diagnostic clues.
Age Range
50-80
Peak Age
65
Gender
Male predominant
Prevalence
Common
ICC arises from malignant transformation of bile duct epithelium. Risk factors include primary sclerosing cholangitis (PSC), hepatolithiasis, Caroli disease, opisthorchiasis, and thorotrast exposure. ICC's most defining histological feature is intense desmoplastic reaction — abundant fibrous tissue forms around tumor cells. This fibrous stroma directly determines imaging findings: (1) peripheral enhancement — viable cellular component and neovascularization at tumor periphery, (2) progressive centripetal filling — contrast slowly accumulates in fibrous stroma, (3) delayed phase enhancement — large extracellular space of fibrous tissue retains contrast, (4) capsular retraction — fibrous tissue contraction pulls the liver surface.
Peripheral hyperintensity + central hypointensity on T2 ('target sign') and progressive filling from periphery to center on contrast-enhanced sequences are the signature findings of ICC. T2 target sign reflects the two-layered structure of peripheral viable cellular component (high water) and central fibrous stroma (low water). Progressive centripetal filling results from delayed contrast retention of fibrous stroma. The combination of these two findings distinguishes from HCC, hemangioma, and metastasis.
Thin, irregular enhancement at the mass periphery in arterial phase. Central portion does not enhance (fibrous stroma has not yet retained contrast). 'Rim' or 'peripheral' enhancement pattern, different from homogeneous APHE in HCC, is characteristic of ICC.
Report Sentence
The mass demonstrates peripheral enhancement in arterial phase, showing an enhancement pattern consistent with intrahepatic cholangiocarcinoma.
Progressive filling of contrast from periphery to center in delayed phase (3-5 minutes). Result of fibrous stroma retaining contrast late. 'Progressive centripetal filling', the most diagnostic enhancement pattern of ICC, is most evident in this phase.
Report Sentence
Progressive enhancement from periphery to center (centripetal filling) is observed in the mass in the delayed phase, consistent with the typical enhancement pattern of cholangiocarcinoma.
Inward pulling of liver capsule adjacent to the tumor (capsular retraction). Liver surface deformity results from contraction of ICC's fibrous stroma. An important clue for non-HCC malignancies (ICC, epithelioid hemangioendothelioma, treated metastasis).
Report Sentence
Capsular retraction is observed adjacent to the mass, supporting the diagnosis of intrahepatic cholangiocarcinoma.
Peripheral hyperintensity (viable tumor tissue, high water content) and central hypointensity (dense fibrous stroma, low water content) on T2-weighted images. This 'target sign' is the characteristic T2 finding of ICC.
Report Sentence
Peripheral hyperintensity and central hypointensity are observed in the mass on T2-weighted sequences, forming the 'target sign'.
Peripheral diffusion restriction on DWI (viable tumor cells) and absence of diffusion restriction in central area (fibrous stroma). Complements the T2 target sign.
Report Sentence
Diffusion restriction is observed at the periphery of the mass on DWI sequences, while no restriction is detected in the central area.
Dilatation of bile ducts proximal to the tumor. ICC originates from bile duct epithelium and obstructs or infiltrates the duct lumen. This finding is not typical in HCC.
Report Sentence
Dilatation of intrahepatic bile ducts proximal to the tumor is observed, an additional finding supporting cholangiocarcinoma diagnosis.
Criteria
Most common type (60-80%). Well-defined or infiltrative mass. Typical peripheral enhancement + centripetal filling pattern is most prominent in this type.
Distinct Features
Single large mass, capsular retraction common, satellite nodules may be present. Bile duct dilatation proximal to tumor.
Criteria
Growth along bile duct wall, thickening the duct wall without forming a distinct mass. Behavior similar to Klatskin tumor.
Distinct Features
Diffuse duct wall thickening and enhancement. Proximal bile duct dilatation is prominent. Seen as duct wall abnormality rather than mass on CT/MR.
Criteria
Papillary or polypoid growth within bile duct lumen. Rarest type. Intraductal tumor + proximal duct dilatation.
Distinct Features
Enhancing polypoid/papillary structure within dilated bile duct. Better prognosis than other types. May overlap with intraductal papillary neoplasm (IPN), the biliary counterpart of IPMN.
Distinguishing Feature
HCC shows homogeneous APHE + nonperipheral washout + enhancing capsule. ICC shows peripheral enhancement + centripetal filling. HCC develops in cirrhosis, ICC usually in non-cirrhotic liver. HCC shows capsular bulging, ICC shows capsular retraction. Bile duct dilatation is rare in HCC, common in ICC.
Distinguishing Feature
Hemangioma shows peripheral nodular (globular) enhancement — different from thin peripheral rim enhancement in ICC. Hemangioma is very bright on T2 ('light bulb sign'), ICC shows target sign. Hemangioma fills completely in delayed phase (centripetal), ICC's fibrous stroma enhances but may not fill completely.
Distinguishing Feature
Neuroendocrine metastasis is hypervascular — shows homogeneous arterial enhancement, different from peripheral enhancement + centripetal filling in ICC. Neuroendocrine metastasis is usually multiple, ICC is usually solitary. History of primary neuroendocrine tumor is distinguishing.
Distinguishing Feature
Epithelioid hemangioendothelioma forms multiple peripheral lesions ('lollipop sign' — lesion at hepatic vein terminus), ICC is usually a solitary large mass. Both may show capsular retraction and delayed enhancement but distribution pattern differs.
Urgency
urgentManagement
surgicalBiopsy
NeededFollow-up
3-monthUnlike HCC, ICC has no non-invasive diagnostic criteria — histopathological confirmation (biopsy) is required. Curative treatment is surgical resection, but only 20-30% of patients are resectable at diagnosis. Prognosis is poor when negative surgical margins (R0) cannot be achieved. Gemcitabine + cisplatin chemotherapy is the standard palliative treatment for locally advanced or metastatic disease. CA 19-9 serum marker can be used for monitoring. Liver transplantation is controversial in ICC — not recommended except in very early stage and highly selected patients. Multidisciplinary approach (hepatobiliary surgery, oncology, radiology) is mandatory.
Surgical resection is the best treatment option when feasible, but most patients present at advanced stage. Distinction from HCC in cirrhotic patients is critical as treatment strategies differ. In LI-RADS, targetoid appearance is classified as LR-M favoring ICC.