CT of hepatic tumors: prevalence and specificity of retraction of the adjacent liver capsule
The purpose of this study was to describe the CT features of capsular retraction of the liver adjacent to hepatic tumors and to test the hypothesis that this finding is specific for malignant hepatic tumors. We first retrospectively reviewed the CT scans of eight patients with pathologically proved malignant hepatic tumors (five secondary and three primary) who had CT scans that showed retraction of the overlying liver capsule. Then, using criteria developed from the first eight cases, we prospectively studied 253 patients with pathologically proved hepatic tumors (75 benign, 178 malignant) to determine the prevalence of retraction of the liver capsule shown by CT and the specificity of this finding for malignant hepatic tumors. CT scans in the first eight patients showed two types of capsular retraction. In seven patients, the retracted liver capsule was smooth and regular. In one patient, capsular retraction was associated with central ulceration extending to and eroding the liver capsule. Four of 253 patients studied prospectively had hepatic tumors with associated capsular retraction (prevalence, 2%). In those four cases, the retracted liver capsule was smooth and regular. All four tumors were malignant (one fibrolamellar hepatocellular carcinoma, two carcinoid tumors, one colorectal metastasis). Capsular retraction of the liver adjacent to hepatic tumors is an uncommon CT finding that appears to be specific for malignant hepatic tumors.