Immunohistochemical evidence of the mesothelial histogenesis of a uterine adenomatoid tumor.

We present rare case of a uterine adenomatoid tumor. In order to characterize the diversity of immunoreactive antigens associated with mesothelial differentiation, we immunohistochemically examined the tumor's epithelioid and myofibromatoid components, as well as the biphasic pattern of its adenomatoid changes. Immunostaining of tumor cells was positive for high- and low-molecular-weight cytokeratins and vimentin. Specific immunoreactions with antibodies against desmin, alpha-actin, and the S-100 protein also were observed. The present adenomatoid tumor can be explained in terms of various transformations and typical alterations in mesothelioma cells: (1) the mesothelial cells had differentiated to epithelial and stromal components, concomitant with the presence of predominant reactive foci; (2) intermediate cells expressed different types of cytoskeletal intermediate filament proteins (IMPs); and (3) the patterns of fibromatoid and leiomyoid differentiation resembled those of a benign mesothelioma of the ovarian or oviductal peritoneum. Our immunohistochemical investigations indicated that the present tumor exhibited the histogenesis of a true mesothelioma, an adenomatoid mesothelioma.