Bright loop appearance; a characteristic ultrasonography sign of early hepatocellular carcinoma

Ultrasonography (US) and computed tomography (CT) are the most effective sc reening methodologies for hepatocellular carcinoma (HCC). In our US screeni ng, 20% of small HCC nodules less than 20 mm in diameter were detected as h yperechoic tumors. Among these hyperechoic HCC nodules, we have often obser ved 'bright loop appearance' (BL) which is defined as hypoechoic nodules in the hyperechoic tumor. In this study, we report that the BL is a sign of d edifferentiation of early stage of HCC with fatty change by US. From 1994 t o 1998, we performed tumor targeting needle biopsy in 938 hepatic nodular l esions. Among them, 284 nodules <20 mm in diameter, histologically diagnose d as HCC, were studied. BL is defined as a hyperechoic tumor containing a h ypoechoic nodule >4 mm in diameter by US. Among 284 nodules, well, moderate ly and poorly differentiated HCC were 183 (64.4%), 100 (35.2%) and 1 (0.4%) , respectively. On US, hypoechoic, isoechoic, and hyperechoic nodules were 188 (66.2%), 32 (11.3%) and 64 (22.5%), respectively. Forty-seven nodules o f 64 hyperechoic HCC nodules <20 mm in diameter, 47 nodules (73.4%) showed fatty changes. Of 64 hyperechoic HCC nodules, we recognized 22 nodules (34. 4%) as BL. The proportion of BL type hyperechoic nodules increased with the tumor size. Two hyperechoic nodules followed by US changed to BL with tumo r enlargement. Histologic examination of a resected HCC with BL showed that hyperechoic HCC nodule represented well-differentiated HCC with fatty chan ge and inner hypoechoic lesion represented moderately differentiated HCC wi thout fatty change. In US screening for HCC, BL was often observed in HCC n odules from 11 to 20 mm in diameter. Histologic examination revealed that B L of HCC on US was associated with tumor progression and indicated dediffer entiation showing moderately differentiated HCC in well-differentiated HCC with fatty change.