The Diagnostic Utility of p16 FISH and GLUT-1 Immunohistochemistry in Mesothelial Proliferations.
Sara E Monaco, Yongli Shuai, Mona Bansal, Alyssa M Krasinskas, Sanja Dacic. University of Pittsburgh Medical Center, PA
Background: Distinction between malignant and benign mesothelial proliferations can be challenging, therefore, ancillary studies have been proposed to improve diagnostic accuracy. Two of the most promising ancillary approaches include immunohistochemical (IHC) assessment of GLUT-1 and FISH assay for the p16 deletion. In this study, the diagnostic utility of p16 FISH and GLUT-1 IHC in the diagnosis of mesothelial proliferations was compared in a large series of surgical and cytopathology specimens.
Design: Surgical pathology and cytopathology cases with a diagnosis of benign/reactive mesothelial cells, atypical mesothelial proliferation, and malignant pleural and peritoneal mesotheliomas were randomly selected from the archives of the University of Pittsburgh Medical Center. The study protocol was reviewed and approved by the institutional review board of the University of Pittsburgh Medical Center. The diagnosis of mesothelioma was rendered based on the morphology, the results of ancillary studies, and the imaging studies.
Results: A total of 154 cases with the diagnosis of benign/reactive (70 cases; 45%), atypical mesothelial proliferation (16 cases;11%), or malignant mesothelioma (68 cases; 44%), including pleural (27 cases; 40%) and peritoneal (41 cases; 60%) mesotheliomas, were included. Of the benign/reactive cases, none had a deletion of p16 and 5 (8%) cases were positive for GLUT-1. Of the mesotheliomas, 40 (59%) had a deletion of p16 (sensitivity 59%; specificity 100%) and 27 (39%) were positive for GLUT-1 (sensitivity 40%, specificity 93%). FISH for p16 was more sensitive in pleural than in peritoneal mesotheliomas (sensitivity 70% vs. 51%). GLUT-1 IHC showed a significantly lower sensitivity for the detection of malignancy in both pleural (sensitivity 56%, specificity 92%) and peritoneal specimens (sensitivity 29%, specificity 100%) (p value 0.004).
Conclusions: Our results demonstrate that FISH testing for the p16 gene deletion is a more sensitive and specific test than IHC testing for GLUT-1, and can be a more reliable ancillary tool to help support the diagnosis of mesothelioma, particularly in small tissue samples.
Tuesday, March 1, 2011 1:45 PM
Platform Session: Section F, Tuesday Afternoon