Primary Hepatic Malignant Fibrous Histiocytoma Mimicking Hepatocellular Carcinoma: Report of Two Cases with Immunohistochemical Detection of Ezrin, and Ultrastructural and K-ras Mutation Analysis

We reported two primary malignant fibrous histiocytoma (MFH) cases (cases 1 and 2) strikingly simulating hepatocellular carcinoma with immunohistochemical (IHC) stains, and ultrastructural and K-ras mutation analysis. Cases 1 and 2 both included only men, aged 65 and 72 years, respectively. Case 1 presented with abdominal pain, fever, and bilateral legs edema. Case 2 was found to have a liver tumor during routine heath examination. Computed tomography scan showed hepatic mass with fine tumor vessels. Case 1 had one 16×15×13cm ³ liver mass with tumor rupture in the right lobe, and case 2 had one 3×2.5×1cm ³ liver tumor in segment 6. Microscopically, the tumors were composed of spindle, pleomorphic, and multinucleated giant cells arranged in storiform, sheet-like, and fascicular patterns. Strong immunoreactivity for CD68 and vimentin in tumor cells in both cases was noticed. Ezrin immunoexpression in tumor tissue from case 1 was diffusely strong; in contrast, case 2 showed sparse and weak ezrin expression in tumor cells. Ultrastructurally, cells with fibroblasts and histiocytic characteristics were present in both cases. K-ras gene analysis of exon 2codon 12 or 13 showed no mutation. This is the first report describing K-ras gene analysis of liver MFH. We emphasize that ezrin immunoreactivity may be correlated with poorer prognosis.