Inflammatory Pseudotumor of the Liver.

Hepatic inflammatory pseudotumor (IPT) describes a mass lesion composed of fibroblasts or myofibroblasts with a dense inflammatory infiltrate comprising lymphocyte, plasma cells, and histiocytes. These lesions are presumed to be an exuberant response to an infectious organism, although in most cases the causative agent is unknown. In specific circumstances, pathologists should consider ancillary techniques to exclude specific infections, such as mycobacteria, Candida, or syphilis. IgG4-related disease may cause a plasma-cell rich IPT. Finally, true neoplasms can mimic IPTs and must be excluded with appropriate ancillary studies, including inflammatory myofibroblastic tumor, follicular dendritic cell tumor, inflammatory angiomyolipoma, Hodgkin lymphoma, and inflammatory hepatocellular carcinoma.