CD146 Expression in Pleural and Peritoneal Mesothelioma
Stephen M Lagana, Robert N Taub, Alain C Borczuk. Columbia University Medical Center, New York, NY
Background: Malignant mesothelioma (MM), of either peritoneum or pleura, is an uncommon cancer. The diagnosis is often difficult to make, in part because of the overlapping morphology of reactive and malignant mesothelial cells. CD146 (also referred to as MUC18) is a transmembrane glycoprotein involved in intercellular adhesion. It has recently been reported to be a highly sensitive and specific marker of malignant, but not reactive, mesothelial cells in a small study of effusion cytology specimens. The staining patterns of CD146 in surgical pathology specimens in either pleural or peritoneal mesothelioma have not been reported.
Design: Tissue microarrays containing 178 mesotheliomas were stained with an antibody to CD146. These cases consisted of 26 pleural mesotheliomas and 152 peritoneal mesotheliomas. Fifty-four whole slide sections with reactive and or hyperplastic mesothelial cells were stained as controls. Cases were considered positive when 5% of the lesional cells showed membranous immunoreactivity. As CD146 is a transmembrane protein, cytoplasmic staining was considered non-specific, and was counted as negative.
Results: Overall, 104 of 178 malignant cases showed membranous CD146 expression, overall sensitivity 58%. Sensitivity was similar amongst the two sites (pleura 50%, peritoneum 60%). The median amount of tumor cells showing immunoreactivity was 40%. Twenty-five of 26 cases with reactive/hyperplastic mesothelial cells in the abdomen were negative for membranous CD146 as were 25 of 28 cases in the thorax. Three of 54 benign cases showed foci of cytoplasmic positivity which was interpreted as negative. Overall specificity was 93%. The positive predictive value was 96%. The negative predictive value was 40%.
Conclusions: The positive predictive value of 96% demonstrates the utility of a positive result for CD146 immunohistochemistry in the distinction of malignant from benign mesothelial cells. There are limitations, however, including weak intensity in some positive cases and rare cytoplasmic staining of unclear significance.
Wednesday, March 21, 2012 9:30 AM
Poster Session V # 296, Wednesday Morning