Differences in early imaging features and pattern of progression on CT between intrahepatic biliary metastasis of colorectal origin and intrahepatic non-mass-forming cholangiocarcinoma in patients with extrabiliary malignancy.

PURPOSE: To assess the differences in early imaging features and progression pattern on CT between intrahepatic biliary metastasis (IBM) and non-mass-forming cholangiocarcinoma (NMFC) in patients with extrabiliary malignancy.

METHODS: This retrospective study included 35 patients who were surgically and pathologically confirmed with IBM (n = 14) or NMFC (n = 21) at the time of or after surgery for extrabiliary malignancy. Two observers evaluated the following aspects of biliary lesions on initial or follow-up CT images: location, characteristics of intrahepatic duct (IHD) dilatation, presence of duct wall thickening, and periductal infiltration lesion or periductal expansile mass.

RESULTS: All IBMs were associated with colorectal cancer (p = 0.032). As early imaging features on CT, smooth tapered localized IHD dilatation without duct wall thickening and peripheral duct involvement were observed significantly more often in IBM, and IHD dilatation with abrupt tapering or irregularity of transition site and bile duct wall thickening were significantly more common in NMFC (all p < 0.05). Regarding progression pattern, periductal expansile mass was present only in IBM, whereas periductal infiltrative lesion was present only in NMFC (p < 0.001).

CONCLUSION: In the differentiation between IBM and NMFC in patients with extrabiliary malignancy, the differences in early imaging features and progression pattern of the two diseases revealed in this study would be helpful for diagnosis.