MALIGNANT PERITONEAL MESOTHELIOMA MIMICKING MESENTERIC INFLAMMATORY DISEASE

A case of malignant peritoneal mesothelioma mimicking mesenteric infla mmatory disease (MID) is presented. The patient had mesenteric and ome ntal lesions characterized at biopsy by extensive fibrosis of fat tiss ue with mild to moderate inflammation. One year later, post-mortem exa mination revealed a well-differentiated epithelial mesothelioma. Immun ohistochemical stains for keratin and vimentin were diffusely positive , whereas EMA showed a membranous staining of scattered cells. CEA, Be r-EP4, B 72.3 and Leu-M1 were negative. In addition, actin monoclonals decorated groups of cells pertaining to the tumoural component. Immun ostains of sections from retrieved paraffin blocks of the previous bio psy showed that the bulk of the spindle-shaped and histiocytic-like ce lls present in the fibrous streams was strongly labeled by low-molecul ar-weight keratin, and coexpressed vimentin and actin. EMA showed a me mbranous staining of sporadic spindle and round cells. The other immun ostains were invariably negative. This immunohistochemical pattern clo sely corresponded to the immunophenotype of the mesothelial tumour det ected at autopsy and was very suggestive of myofibroblastic/submesothe lial cell origin. The quantitative evaluation of silver nucleolar orga nizer regions (Ag-NORs) demonstrated high levels of cell proliferation in both surgical and autopsy tissue samples.