CT DIAGNOSIS OF EARLY HEPATOCELLULAR-CARCINOMA - SENSITIVITY, FINDINGS, AND CT-PATHOLOGICAL CORRELATION

OBJECTIVE. The purpose of this study was to determine the sensitivity of CT in detecting early hepatocellular carcinoma and to evaluate its CT appearance. An early hepatocellular carcinoma is a nodular lesion w ith no fibrous capsule composed of well-differentiated tumor histologi cally. It differs from a small hepatocellular carcinoma, which is an o vert tumor that is moderately to poorly differentiated and had a fibro us capsule. Size is not a criterion for distinguishing between early a nd small hepatocellular carcinomas. MATERIALS AND METHODS. Thirty-one patients with 39 histopathologically proved early hepatocellular carci nomas (mean diameter, 1.7 cm) found by sonography, MR imaging, and/or intraoperative sonography were included in a retrospective study, We r eviewed unenhanced CT scans of the entire liver in 30 patients (37 les ions) and early and late (35 sec and 5 min after the beginning of inje ction of contrast material) contrast-enhanced CT scans of the entire l iver in all 31 patients (table incremental CT in 21; helical CT in 10; 39 lesions), Eighteen histologically proved small hepatocellular carc inomas (less than or equal to 3 cm; mean diameter, 2.3 cm), present in the same patients, served for comparison, Histopathologically, nine p atients had chronic hepatitis, and 22 had cirrhosis. RESULTS. The over all sensitivity of CT in detecting early hepatocellular carcinoma was 56%, These tumors were usually isodense with respect to surrounding li ver on unenhanced, early enhanced, and late enhanced CT scans (iso-iso -iso). This pattern was seen in 17(46%) of 37 lesions; thus, these 17 histologically proved early hepatocellular carcinomas were not detecte d with CT, An iso-iso-low density pattern was recognized in eight (22% ), a low-low-law pattern in seven (19%), and several different pattern s in five (13%) of the 37 lesions, Only two (5%) of 39 early hepatocel lular carcinomas had a high-density appearance on early enhanced CT sc ans, In comparison, the most common pattern of small overt hepatocellu lar carcinomas on CT scans was low-high-low, seen in 17 lesions (94%) detected with CT, When the density of lesions on unenhanced CT scans w as compared with the histopathologic appearance of the masses, low-den sity lesions showed mild to moderate fatty change and isodense lesions showed no or minimal fatty change (p = .006). CONCLUSION. The sensiti vity of CT in detecting early hepatocellular carcinoma is poor (56%), However, the diagnosis of early hepatocellular carcinoma should be con sidered if CT scans show a small lesion with an iso-low or low-low den sity enhancement pattern on early and late contrast-enhanced CT scans, respectively, in patients with chronic liver disease.