The use of immunohistochemistry to distinguish reactive mesothelial cells from malignant mesothelioma in cytologic effusions.
BACKGROUND
The distinction of benign from malignant mesothelial proliferations in cytologic specimens can be problematic. In this study, the authors investigated the utility of immunohistochemical (IHC) markers in making this distinction.


METHODS
Archival paraffin-embedded cell blocks of pleural and peritoneal fluids from 52 patients with malignant mesothelioma (MM) and 64 patients with reactive mesothelial hyperplasia (MH) were retrieved. IHC stains included desmin, epithelial membrane antigen (EMA), glucose-transport protein 1 (GLUT-1), Ki67, and p53.


RESULTS
Desmin was positive in 84% (54 of 64) cases of reactive MH and in 6% (3 of 52) of MM cases (P < .001). EMA was positive in 9% (6 of 64) of benign and 100% (52 of 52) of malignant cases (P < .001). GLUT-1 was positive in 12% (5 of 43) of benign and 47% (7 of 15) of malignant cases. Ki67 showed strong nuclear positivity in >40% of mesothelial cells in 9% (6 of 64) of benign and 16% (8 of 49) of malignant cases (P = .38). p53 showed strong nuclear positivity in 2% (1 of 46) of benign and 47% (7 of 15) of malignant cases (P < .001). EMA positivity and desmin negativity were found in 2% (1 of 64) of reactive MH cases and 98% (49 of 52) of MM cases (P < .001). EMA negativity and desmin positivity were found in 86% (55 of 64) of reactive MH cases and 0% of MM cases.


CONCLUSIONS
The combination of positive EMA and negative desmin strongly favors MM; conversely, a combination of negative EMA and positive desmin favors a reactive process. Likewise, strong membranous positivity for GLUT-1 and/or strong nuclear staining for p53 favors a mesothelioma. Ki67 proliferative index showed no significant difference between reactive MH and MM cases.
Hasteh
Farnaz
F
Department of Pathology, University of California-San Diego Medical Center, 200 W. Arbor Drive, La Jolla, CA 92103, USA. fhasteh@ucsd.edu
Lin
Grace Y
GY
Weidner
Noel
N
Michael
Claire W
CW
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001202:Ascitic Fluid / Q000378:metabolism*; D015415:Biomarkers / Q000378:metabolism; D003893:Desmin / Q000032:analysis; D004848:Epithelium / Q000473:pathology*; D027342:Excitatory Amino Acid Transporter 2 / Q000032:analysis; D005260:Female; D006801:Humans; D006965:Hyperplasia / Q000473:pathology; D007150:Immunohistochemistry; D008297:Male; D008654:Mesothelioma / Q000175:diagnosis*; D008875:Middle Aged; D018396:Mucin-1 / Q000032:analysis; D010996:Pleural Effusion / Q000378:metabolism*; D016159:Tumor Suppressor Protein p53 / Q000032:analysis
D015415:Biomarkers; D003893:Desmin; D027342:Excitatory Amino Acid Transporter 2; D018396:Mucin-1; D016159:Tumor Suppressor Protein p53