INCIDENTAL FOCAL HEPATIC MASS

Findings

CT revealed a hypervascular mass in the sixth segment of the liver during arterial enhancement (Figure 1a). This lesion exhibited slight hypointensity on pre-contrast T1 weighted MRI (Figure 2a). The anterior portion of this lesion demonstrated a similar degree of enhancement  to the surrounding liver parenchyma (Figure 2b, arrow), while the posterior portion exhibited reduced enhancement (Figure 2b, arrowhead).

Diagnosis

The patient underwent the right posterior segmentectomy. The surgical specimen was a well-demarcated, round mass measuring 4.5 cm in diameter (Figure 3a).

Histological diagnosis of both portions was moderately differentiated hepatocellular carcinoma (HCC). However, the microscopic specimen obtained at the junction of the tumour consisted of two different subtypes (Figure 3b): pseudoglandular (Figure 3c) and microtrabecular (Figure 3d). On immunochemical staining, the tumour cells were positive for Glycan, CD13 and CD34, but negative for AFP and CK19.

Discussion

HCC occurs frequently in patients with chronic liver disease, which is related with viral hepatitis B and C. Gd-EOB-DTPA is a newly developed hepatocyte-specific  agent, which transports into the hepatocyte through organic anion transporting polypeptides (OATPs) and is excreted into bile through canalicular multiorganic anion transporters [1, 2]. Because Gd-EOB-DTPA uptake is usually reduced in HCC cells, this agent may help estimate histological grading [3]. To the best of our knowledge, there have been few reports of the simultaneous high and low accumulation of Gd-EOB-DTPA in solitary and moderately differentiated HCC. Recently, it has been proposed that OATP 1B1/3 mediates the uptake of Gd-EOB-DTPA from sinusoid to tumour, whereas the multidrug resistance-associated protein 2 (MRP2) mediates the secretion of Gd-EOB-DTPA from tumour to lumen [4].

Although the histological findings of most tumour cells display some degree of Gd-EOB-DTPA content, HCCs exhibit different levels of enhancement on Gd-EOB-DTPA-enhanced MRI according to the positive expression of the two transporters. Therefore, awareness of these properties may contribute to the accurate diagnosis of HCC.