MR imaging of small hepatocellular carcinoma (< or = 20 mm)--correlation with vascularity and histological features

We have evaluated the efficacy of magnetic resonance (MR) imaging for detecting hepatocellular carcinoma less than 20 mm in diameter (sHCC). This study involved 72 cases of sHCC tumors which were also investigated by angiography and histology. These cases were retrospectively examined for correlations between tumor stain (vascularity) on angiography, histological features (fat deposition, clear cells and the grade of differentiation) and the findings on T1 and T2 weighted MR imaging. The sHCC detection rate by MR imaging was 73.6% (53 cases) and by angiography was 59.7% (43 cases). Thirty-five cases were detected both the MR imaging and by angiography. The main MR imaging patterns were hypo to isointense on T1 weighted images (T1WI) and hyperintense on T2 weighted images (T2WI) in 22 cases, and hyperintense on both T1WI and T2WI in 7. In 18 cases which were not demonstrated by tumor staining on angiography, the main MR imaging patterns were hyperintense on T1WI and isointense on T2WI in 14. The histological features included fat deposition in 22 cases, 20 cases of which were hyperintense on T1WI, and 10 of these 20 were hyperintense on both T1WI and T2WI. Fat deposition was marked in 9. According to the grade of differentiation, 23 of the 26 cases with well differentiated HCC tumors were hyperintense on T1WI, and 21 of the 27 cases with moderately to poorly differentiated HCC were hypo to isointense on T1WI and hyperintense on T2WI. sHCC was visualized by MR imaging, reflecting vascularity, fat deposition and the grade of differentiation. In particular, MR imaging is useful for a differential diagnosis between the well differentiated HCC and the moderately to poorly differentiated HCC, and useful for the diagnosis of an early HCC.