[Inflammatory pseudotumor of the liver. Morphologic and cytophotometry studies and differential diagnosis].

Inflammatory pseudotumors of the liver are extremely rare. Worldwide only 50 cases have been described so far. In lung tissue, their incidence is higher, with 119 cases being published. Etiological factors are still a matter of debate; reactive inflammatory processes have recently been proved by immunohistological and cytophotometric studies. This seems to be true for both liver and lung locations of inflammatory pseudotumors. Considerable morphological heterogeneities, conspicuously varying from one case to another, reflect the numerous synonyms that have been created for this condition, i.e., plasma cell granuloma, xanthoma, fibroxanthoma, histiocytoma, plasmacytoma, solitary "mast cell tumor" and pseudoneoplastic pneumonia, just to number a few of them. This multicolored morphology explains the difficulties in histologic diagnosis, especially if needle biopsies or frozen sections are submitted to pathology. Differential diagnosis of an inflammatory pseudotumor of the liver needs to include fibrohistiocytic neoplasia if spindle-cell-shaped areas are included or, on the other hand, parenchymal infiltrates of the nodular sclerosing type of Hodgkin's granuloma. Immunohistological investigations do not allow final decisions since spindle-shaped cells within pseudotumours can express vimentin and/or desmin as well. Such histological cases should always include the excision of a piece of liver tissue of sufficient size to comfortably allow for the recognition of the multicellular composition and morphological heterogeneity of this process.