A sub-centimeter HCC with bright loop appearance diagnosed by contrast-enhanced ultrasonography.

Detection of a hepatocellular carcinoma (HCC) in the early stage is critical, as clinical stage influences treatment selection and patient prognosis. Carcinogenetic development of an HCC is a multi-step process, and a differential diagnosis between a dysplastic nodule and a well-differentiated HCC is often difficult. A bright loop appearance is a significant finding that indicates disappearance of fatty deposition in the central area of the nodule during the progression toward HCC, however such a finding is rare in cases of sub-centimeter-sized HCCs. We encountered a case of HCC that developed a bright loop appearance on ultrasound (US) without enlargement approximately 2 years after diagnosis as a dysplastic nodule. Moreover, the hypoechoic area in the center of the nodule showed an HCC pattern in contrast enhanced US with Sonazoid™. Vascularity in the nodule could not be observed on dynamic contrast-enhanced CT or Gd-EOB-DTPA-enhanced MRI. When a change in the intranodular echo pattern is observed in sub-centimeter-sized nodules, examination of intranodular vascularity by contrast-enhanced US is important to evaluate borderline lesions.