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Page 6 of 15 Della Corte et al. Hepatoma Res 2022;8:5 https://dx.doi.org/10.20517/2394-5079.2021.103

they allow detection of both distant and nodal metastasis using 18F-FDG. Potential caveats may be false
[36]
positives in cases with biliary inflammation and false negatives in mucinous CC .
peCC
The most common peCC is the periductal infiltrating type characterized by elongated strictures with
irregularly visible walls on imaging and delayed enhanced duct dilation. Imaging assessment of tumor
[37]
infiltration in the deeper mucosal layers of the bile ducts is challenging . In addition, imaging
characteristics of peCC are similar to those of other hepatic diseases, benign and malignant, and differential
diagnosis becomes cardinal for correct patient management. In these cases, evaluation using contrast
enchanced-CT or MRI-MRCP is recommended. DWI seems to be able to differentiate malignant strictures
[38]
in extrahepatic disease , with contrasting views of T1 sequences in peCC. 18F-FDG PET/CT has shown to
be able to differentiate between benign and malignant strictures [39,40] in larger lesions [41,42] .

Surgical assessment on imaging, even more in the light of new advances in surgical techniques and
perioperative management which allow a larger cohort of patients to pursue this curative indication, is also
challenging. Extent of involvement of the bile ducts (proximal margin involvement and longitudinal extent)
and patient intrinsic patient characteristics are major differentials. Imaging using different CT modalities
(i.e., CT alone, CT with direct cholangiography, or CT with reconstruction) have been able to confirm the
documented ability of MRCP-dynamic MRI to identify secondary confluence involvement with comparable
results . The description of local extent of tumor invasion, anatomy of the biliary tree and association of
[37]
tumor extent within the liver is mandatory for optimal resectability assessment.

ICC
Mass-forming ICCs are the most common morphological subtype of ICCs. On imaging they appear as large
non-capsulated masses with associated peripheral dilation of bile ducts and may appear hypervascular
similarly to HCC. Further characteristic imaging features include capsule retraction. Depending on their
stromal component, generally characterized by fibrosis following desmoplastic reaction in the central
portion, they may exhibit a typical late central enhancement with peripheral hypoenhancement. In several
cases, additional nodules in proximity of the lobulated or irregular mass forming nodules and hepatic
metastases are also visible. Since pattern of enhancement can vary, differential diagnosis with HCC is often
challenging even when gadoxetic acid is used as contrast agent [43-45] . However, MRI may address towards
diagnosis of ICC when “target appearance” is noted on diffusion weighted imaging or in post-contrast late
hepatospecific phase. In the former, DWI images at high b-value will show an hyperintense rim
surrounding a central area of hypointensity. In the latter, a central cloud-like hyperintensity will be
surrounded by a rim of peripheral hypointensity. In both cases, these typical appearances reflect the
histological components of ICC, characterized by a peripheral area of hypercellularity and a central
hypocellular area dominated by fibrosis. Histopathology is considered mandatory in order to confirm
imaging features which may resemble other benign or malignant (combined) lesions.

Prognostic value of CT and MRI
Recently, studies have demonstrated that preoperative CT and MRI features - of ICC may predict overall
survival and/or disease-free survival after surgical resection or loco-regional therapies.

In ICC, studies suggest that extended areas of arterial hyperenhancement and hyperintense signal on
DWI [46-48] show a favorable prognosis as opposed to tumors characterized by hyper- or isointense signal on
the hepatobiliary phase or with extended areas of delayed phase enhancement reflecting a higher fibrous
[49]
content . This is consistent with the histopathological observation that patients with scirrhous type ICC,
[50]