A case of diffuse-type primary hepatic lymphoma mimicking diffuse hepatocellular carcinoma

Primary hepatic lymphoma (PHL) is a very rare disease, especially in the diffuse type. We report a case of a middle-aged man with hepatitis C virus infection who developed diffuse-type PHL mimicking diffuse hepatocellular carcinoma (HCC). Contrast-enhanced computed tomography (CT) and magnetic resonance imaging showed diffusely infiltrated hypovascular lesions throughout the liver, but no intrahepatic portal venous thrombus was observed. Diffusion-weighted imaging and ¹⁸F-FDG positron emission tomography/CT, respectively, showed a very low apparent diffusion coefficient value and high FDG uptake. These findings were more suggestive of diffuse-type PHL than diffuse HCC. Liver biopsy examination confirmed a diagnosis of diffuse large B-cell lymphoma. Systemic staging revealed no evidence of nodal or bone marrow involvement, so PHL was diagnosed. The patient was treated with chemotherapy and achieved complete remission. We suggest that a combination of image modalities may enable differentiation of diffuse-type PHL from diffuse HCC.