DESMIN EXPRESSION IN REACTIVE MESOTHELIUM - A POTENTIAL AID IN EVALUATION OF GYNECOLOGIC SPECIMENS

Desmin is a marker of smooth and striated muscle, but evidence is accu mulating that it may be expressed by human mesothelium. The aim of thi s study was to describe desmin expression in normal, reactive, and hyp erplastic peritoneal mesothelium, and to evaluate its potential use as a marker fur differentiating between epithelial and mesothelial proli ferations. We immunohistochemically studied 27 tissue specimens (from 22 patients) with reactive mesothelium, including omentum (n = 14), fa llopian tubes (n = 7), ovaries (n = 3), ascitic fluid (n = 1), and per itoneal washings (n = 2). Ovarian surface epithelium (OSE) from 9 case s and 28 ovarian surface epithelial tumors was evaluated for compariso n. The desmin expression pattern in the mesothelium, which was similar to but less consistent than that of cytokeratins, was evident in flat and reactive mesothelium, including hyperplastic mesothelial sheets a nd mesothelium entrapped in clefts. Mesothelial pseudoglandular struct ures, present in three cases, were predominantly negative for desmin. Desmin expression was observed in the OSE in 4 of 9 cases but not in a ny mullerian-derived epithelium or mullerian type tumor. Thus, in cont rast to cytokeratins, desmin discriminated mesothelial cells from mull erian type epithelia. Compared with vimentin, desmin discriminated mes othelial cells from other tissues except muscle cells. We conclude tha t desmin may be used in addition to cytokeratins and vimentin as a mar ker of peritoneal mesothelium.