[376] EZH2, a Unique Marker of Malignancy in Effusion Cytology

Huimiao (Mia) Jiang, Raavi Gupta, Jonathan Somma. SUNY Downstate Medical Center, Brooklyn, NY

Background: Distinguishing reactive mesothelial cells from metastatic disease in effusion cytology can be challenging at times. We currently use of a panel of immunocytochemical (ICC) markers for select cases including MOC-31 and BerEp4, but difficulties still exist, especially when the questionable cells are scarce. Enhancer of zeste homologue 2 (EZH2), a member of the Polycomb group of genes, plays important roles in epigenetic silencing and cell cycle regulation and is upregulated in a wide variety of malignancies. Thus, we hypothesized that EZH2, which to our knowledge has not yet been reported on cytology material, might serve as a unique marker of malignancy in morphologically equivocal effusion specimens.
Design: A retrospective search over a two year period ending 6/30/2011 was performed and clear cut effusion cases were selected as follows. Diagnoses were confirmed by review of cytomorphology and also had to be supported by clinical history, radiology, and pathology as applicable. For benign cases, those with a history of malignancy or a significant concern for malignancy were specifically excluded. Cases without sufficient cells of interest remaining on cell block were also excluded. The expression of EZH2 was assessed by ICC after optimization for cytologic material including antigen retrieval with EDTA and using a 1:10 dilution of monoclonal anti-EZH2 (Biocare Medical, Concord, CA). An ICC staining assessment method that has previously been applied to cytology effusions was adopted where a positive result was defined as appropriate (i.e. nuclear) staining in at least 5% of the cells of interest.
Results: In total, 27 effusions were analyzed including 9 benign (5 pleural and 4 ascitic) and 18 malignant (9 pleural, 8 ascitic, and 1 pericardial) with primary sites as follows: 3 lung, 3 breast, 3 ovary, 5 uterus, 1 stomach, 1 pancreas, 1 kidney, and 1 of unknown primary. All malignant cases were metastatic carcinomas except for one, an epithelioid endometrial stromal sarcoma. The benign cases were all negative for EZH2, and 16 of 18 malignant effusions were positive; the pancreatic and renal primaries were the outliers. As a solitary ICC marker, EZH2 exhibited a sensitivity of 89% and a specificity of 100%.
Conclusions: EZH2 functioned as a unique and accurate marker of malignancy in this series of effusions. It demonstrated comparable sensitivity and improved specificity relative to published data for MOC-31 and BerEp4. After confirmation in larger studies, EZH2 may prove to be of great value in routine diagnostic work.
Category: Cytopathology

Tuesday, March 20, 2012 9:15 AM

Platform Session: Section F, Tuesday Morning

 

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