Unmasking infiltrative hepatocellular carcinoma: a pictorial essay

Infiltrative hepatocellular carcinoma (HCC) is an aggressive macroscopic growth pattern of HCC characterized by diffuse parenchymal involvement, heterogeneous neovascularity and a high risk of vascular invasion. Early radiologic detection might be challenging because tumor signal and enhancement often blend into the heterogeneous cirrhotic liver background, leading to delayed diagnosis and unfavorable prognosis. This pictorial essay reviews the pathophysiologic mechanisms underlying the imaging appearance of infiltrative HCC and highlights the central role of multiphasic CT and MRI in its evaluation. MRI is particularly valuable in ill‑defined disease due to superior tissue characterization related to higher contrast resolution achieved by diffusion‑weighted imaging (DWI), subtraction techniques, T1‑ and T2‑weighted sequences and hepatobiliary contrast-enhanced imaging. Typical imaging features include T1 hypointensity, T2 hyperintensity, variable arterial enhancement with heterogeneous washout, diffusion restriction, bulging contours, satellite nodules and tumor in vein. This essay highlights patterns of infiltrative HCC spread and key complications, such as venous tumor thrombosis and arteriovenous fistula, and reviews important differential diagnoses. Recognizing these imaging characteristics of infiltrative HCC supports accurate LI‑RADS categorization, enables earlier diagnosis, guides appropriate use of biopsy for indeterminate lesions and promotes optimized multidisciplinary management, particularly in patients awaiting liver transplantation.