Limitations of imaging diagnosis for small hepatocellular carcinoma: comparison with histological findings

The purpose of this study was to clarify the value and limitation of imaging modalities for diagnosing small hepatocellular carcinoma (HCC).

Nodules (n = 207) with diameters of 20 mm or less detected by periodic ultrasonography and computed tomography in 139 patients with chronic liver disease were investigated with digital subtraction angiography (DSA) and magnetic resonance imaging (MRI). These findings were compared with histological findings.

Histological diagnoses were adenomatous hyperplasia (AH, n = 27), well-differentiated HCC (n = 99), moderately differentiated HCC (n = 79) and poorly differentiated HCC (n = 2). We compared two groups: group A (n = 62), nodules of 10 mm diameters or less; and group B (n = 145), nodules 11-20 mm. Adenomatous hyperplasia accounted for approximately 30% of group A, but was difficult to diagnose with imaging modalities alone. We diagnosed those nodules showing hypervascular staining on DSA or hyperintensity on MRI T2-weighted images as HCC. Imaging alone was sufficient to diagnose HCC in 58% of the well-differentiated nodules and 87% of the moderately and poorly differentiated nodules (P < 0.01). It was possible to diagnose HCC by imaging alone in 60% of all nodules or 45% of group A and 68% of group B (A vs B, P < 0.005).

With decreasing differentiation and increasing diameter of nodules, the use of imaging modalities to diagnose HCC improved. Tumour biopsy was required to diagnose 55% of the cases in group A and 32% of the cases in group B.