[461] Value of PAX8 and WT1 Immunostains in the Detection of Metastatic Ovarian Carcinoma in Effusion Specimens.

Lichao Zhao, Nour Sneige, Yun Gong. The University of Texas MD Anderson Cancer Center, Houston

Background: Diagnosing metastatic ovarian carcinoma (OC) in effusion samples based solely on cytomorphologic features can be challenging, because the tumor cells can resemble reactive mesothelial cells. WT1 immunostaining is often used to aid diagnosis in this setting. Recently, PAX8 immunostaining was found to be positive in most primary OC; however, its role in detecting metastatic OC in effusion samples has not been well defined. The aim of this study was to compare the diagnostic value of PAX8 immunostaining with that of WT1 immunostaining.
Design: Between January 2002 and January 2010, we identified 68 peritoneal or pleural effusion samples with metastatic OC. All patients had history of primary OC confirmed by surgical excision but no history of other malignancy. Cell block sections (n=45) or direct smears (n=23) were used for immunostains for PAX8 and WT1. Nuclear staining in >5% tumor cells was considered positive.
Results: Histologic diagnoses of the 68 primary OC included serous carcinoma (SC) in 52 cases (46 high-grade and 6 low-grade), clear cell carcinoma in 5, borderline mucinous neoplasm in 1, malignant mixed Mullerian tumor (MMMT) in 1, and carcinoma with mixed components of SC, endometroid, clear cell, transitional, and undifferentiated carcinoma in 9. PAX8 staining was positive in 57 (84%) cases, and WT1 staining was positive in 58 (85%) cases (Table1); 50 (74%) cases were positive for both markers. Combination of both markers yielded a detection rate of 94% (64/68). Detection rates on the cell block and on smear were 91% and 78% for PAX8, and 82% and 83% for WT1. Notably, in 21 (31%) cases, WT1 was also positive in the background mesothelial cells.

Table 1. Detection Rate for Metastatic Ovarian Cancer in Effusion Samples by PAX8 and WT1 Staining
  Number (%) of Positive Effusion Sample
Surgical diagnosis of primary ovarian tumorTotal CasesPAX8WTI
High-grade SC4642 (91%)42 (91%)
Low-grade SC63 (50%)6 (100%)
Clear cell carcinoma55 (100%)1 (20%)
Borderline mucinous neoplasm10 (0%)0 (0%)
MMMT11 (100%)1 (100%)
Carcinoma, mixed96 (67%)8 (89%)
Total6857 (84%)58 (85%)

Conclusions: PAX8 and WT1 had similar overall detection rates for metastatic OC in effusion samples. PAX8 was more readily than WT1 to detect clear cell carcinoma but was less effective at detecting low-grade SC. Combining PAX8 and WT1 substantially increased the diagnostic accuracy. Both cell block sections and smears can be used for PAX8 and WT1 staining.
Category: Cytopathology

Wednesday, March 2, 2011 1:00 PM

Poster Session VI # 72, Wednesday Afternoon


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