Fatty hepatocellular carcinoma: radiofrequency ablation--imaging findings.

Purpose: To describe the imaging features during follow-up after radiofrequency (RF) ablation of fat-containing hepatocellular carcinoma (HCC). Materials and Methods: Institutional review board approval was obtained; informed consent was waived. A retrospective search in an electronic radiologic archive was performed for a 40-month period between February 2004 and May 2007 to identify patients who had undergone RF ablation of fat-containing HCCs. The presence of intratumoral fat was determined at imaging (magnetic resonance or computed tomography) prior to the RF procedure; eight fat-containing HCCs, which had a mean size of 25 mm (range, 20-30 mm), were found. Images during follow-up were reviewed and compared with images prior to RF ablation to determine changes in fat content, complete or partial ablation, and local tumor progression. Tumor response was on the basis of assessment of lesion characteristics and enhancement for a follow-up of at least 6 months. Results: Persistent fat content was found at imaging in all ablation zones. Six patients were considered to have completely ablated tumors (mean follow-up, 16 months; range, 6-29 months), and two patients had local progression (mean follow-up, 18 months; range, 14-22 months). In the ablation zone of completely ablated tumors, the fat content progressively decreased (n = 4) or was unchanged during follow-up (n = 2). In the two tumors with local progression, the fat portion enlarged (n = 1) or did not change after ablation (n = 1). Conclusion: Persistence of fat in the ablation zone during imaging follow-up after RF ablation of fat-containing HCCs does not necessarily indicate treatment failure. Changes in fat content of the ablation zone during follow-up (increase or decrease in size) could be used as additional criteria to determine success or failure of RF ablation in fat-containing HCC. (c) RSNA, 2009