Infiltrative hepatocellular carcinoma: comparison of MRI sequences for lesion conspicuity.

AIM: To characterize the magnetic resonance imaging (MRI) features of infiltrative hepatocellular carcinoma (I-HCC), with emphasis on its relative conspicuity on different sequences.
MATERIALS AND METHODS: Nineteen patients exhibiting HCC with non-mass-like appearance and ill-defined margins, and who died within 1 year following diagnosis of I-HCC, were included. For each sequence, two observers independently assessed the lesion's signal intensity relative to benign liver as well as subjective visual conspicuity. The observers also selected the sequence exhibiting the greatest visual conspicuity. A separate radiologist placed regions of interest to measure tumour-to-liver contrast for each lesion. Tumour size and clinical features were also assessed.
RESULTS: Eighteen of the 19 patients exhibited central portal vein tumour thrombus; eight of the 19 patients had metastatic disease. All I-HCC measured over 5 cm. The two observers identified hyperintensity on T2-weighted imaging (WI) in 19 and 19 cases, hyperintensity on high b-value diffusion-weighted imaging (DWI) in 18 and 19 cases, arterial-phase hyperintensity in six and 10 cases, and venous-phase hypo-intensity in 17 and 16 cases. T2WI, DWI, and venous-phase images exhibited significantly greater subjective visual conspicuity than arterial-phase images for both observers (all p ≤ 0.040). Also, T2WI and DWI tended to exhibit greater tumour-to-liver contrast than arterial- and venous-phase images (all p ≤ 0.055). The arterial-phase was not selected as having greatest conspicuity for any case by either reader.
CONCLUSION: I-HCC is an aggressive form of HCC that is often less conspicuous on arterial-phase images than typical mass-forming HCC; T2WI and DWI may be more useful sequences for its diagnosis. Awareness of the distinct imaging features of I-HCC may be important for proper diagnosis.