Multiphasic MDCT Enhancement Pattern of Hepatocellular Carcinoma Smaller Than 3 cm in Diameter: Tumor Size and Cellular Differentiation

OBJECTIVE. The purpose of this study was to evaluate according to size and degree of cellular differentiation the multiphasic MDCT enhancement pattern of hepatocellular carcinoma (HCC) smaller than 3 cm in diameter in patients with cirrhosis. MATERIALS AND METHODS. In 155 consecutively registered patients (126 men, 29 women; mean age, 58.4 years), 204 pathologically proven HCCs smaller than 3 cm were detected at multiphasic MDCT. Three radiologists in consensus classified the relative attenuation of the tumors compared with the surrounding liver parenchyma as hyperattenuation, isoattenuation, or hypoattenuation on biphasic (n = 86) and triphasic (n = 69) CT scans. RESULTS. The prevalent enhancement patterns of HCC differed depending on tumor size. The prevalent pattern of HCC measuring 20-29 mm was arterial hyperattenuation with venous washout (47%, 47/101). The prevalent enhancement patterns of HCC smaller than 10 mm and HCC measuring 10-19 mm were isoattenuation during the arterial and portal venous phases (29%, 6/21) and hyperattenuation and isoattenuation during the arterial and portal venous phases (33%, 27/82). The typical HCC enhancement pattern (arterial hyperattenuation with venous washout) was identified in 48% (67/141) of the moderately and poorly differentiated HCCs and in 13% (8/63) of well-differentiated HCCs. CONCLUSION. The prevalent enhancement patterns of HCC smaller than 3 cm on multiphasic MDCT scans differed depending on tumor size and cellular differentiation. HCCs smaller than 2 cm and well-differentiated HCCs frequently had atypical enhancement patterns.