CT presentations of hepatic lymphoma: what radiologists need to know.

Hepatic lymphomas are rare malignancies that are classified as either primary hepatic lymphoma (PHL) or secondary hepatic lymphoma (SHL). They can present with several CT patterns, including a solid focal lesion, multifocal lesions, a diffuse pattern, or a porta hepatis lesion. PHLs most often present as solid lesions, whereas SHLs are commonly multifocal. On CT, they typically appear as hypovascular, hypoattenuating masses that may show central low-density necrosis and demonstrate only minimal enhancement compared to the surrounding parenchyma. Rim enhancement may be seen, creating a "target sign." These lesions often exhibit an infiltrative growth pattern, encasing vessels, and biliary structures without causing compression. Although rare, it is important to include lymphoma in the differential diagnosis of a hypodense liver lesion. This pictorial essay illustrates the CT patterns and features of hepatic lymphoma that will assist radiologists in evaluating it as a possible diagnosis.