Fibrolamellar hepatocellular carcinoma: multiphasic CT features of the primary tumor on pre-therapy CT and pattern of distant metastases

The aim of our study is to describe the multiphasic CT features of fibrolamellar hepatocellular carcinomas (FLHCCs) and pattern of distant metastases.

33 patients (mean age 28 years: 17M/16F) with pathologically confirmed FLHCC and pre-treatment multiphasic CT were included in the study. Two abdominal radiologists evaluated the multiphasic CT imaging features of these 33 FLHCC patients in consensus.

Solitary hepatic mass was seen in 67% (22/33). Mean tumor size was 11.3 cm (range 4.6–22 cm). Tumor was well-defined in 64% (21/33). In the pre-contrast CT, 91% (30/33) were hypoattenuating. Central stellate scar was present in 73% (24/33). In FLHCC having central stellate scar, calcification within the central scar was seen in 88% (21/24). In the hepatic arterial phase, 82% (27/33) were hyperattenuating relative to liver. In the portal venous phase, 36% (12/33) were hyperattenuating, 46% (15/33) were isoattenuating, and 18% (6/33) were hypoattenuating. In the delayed phase images, 24% (8/23) were hyperattenuating, 67% (22/33) were isoattenuating, and 9% (3/33) were hypoattenuating. Delayed enhancement of the central stellate scar was seen in 12% (4/33). Distant metastases were seen in 54% (18/33). The most common site of metastases was lungs and was seen in 89% (16/18) of the patients with metastatic disease.

FLHCC typically manifests as a large, solitary mass demonstrating heterogeneous hypervascular enhancement in the arterial phase. Most tend to be isoattenuating in delayed phase. Central stellate scar with internal calcification is a useful imaging feature that can help in the diagnosis of FLHCC. Lungs are the most common site of distant metastases in FLHCC.