[1206] Pax 8 Is a Reliable Marker in Making a Tissue Diagnosis of Primary Epithelial Ovarian/Peritoneal Carcinomas for Neoadjuvant Chemotherapy

Teodulo G Meneses, Dan Wang, Song Liu, Faith Ough, Paulette Mhawech-Fauceglia. University of Southern California, LAC+USC Medical Center, Los Angeles, CA; Roswell Park Cancer Institute, Buffalo, NY

Background: Neoadjuvant chemotherapy (NAC) followed by interval debulking surgery is an alternative approach in the management of patients with advanced stage epithelial ovarian carcinoma (EOC)/peritoneal carcinomas (PC) compared to the traditional debulking surgery followed by chemotherapy. Therefore, a tissue diagnosis for malignancy confirmation is crucial. However, due to the wide differential histologic diagnoses, an accurate diagnosis could be challenging. Herein, we are planning to evaluate the utility of the transcription factor protein, PAX8, in the diagnosis of primary EOC/PC for patients eligible for NAC.
Design: This is a retrospective study in which our database was searched for patients diagnosed with EOC/PC who received NAC followed by debulking surgery during a seven-year period (2004-2011). Immunohistochemistry (IHC) was performed on paraffin-embedded tissue from 96 cases (53 EOC/PC and 43 non-ovarian carcinomas). The IHC slides were blindly reviewed and the results of the PAX8 staining intensity were reported as positive (weak, moderate, and strong) or negative (no staining observed).
Results: For EOC/PC cases, 36 cases were biopsy specimens and 17 cell blocks prepared from ascitic fluid (n=10), pleural fluid (n=4) and supraclavicular lymph node aspiration (n=3). The histology was as follows; 45 serous, 3 endometrioid, 3 mucinous, 1 clear cell and 1 carcinosarcoma subtypes. As for non-ovarian carcinomas, the tissue distribution was as follows; cell block from ascitic fluid (n=1), whole section from metastatic adenocarcinoma to the ovary (n=12) and biopsies form various sites (n=30). Overall, PAX8 was positive in 53/96 (55%) cases and negative in 43/96 (45%) cases. 51/53 (96%) of EOC/PC were positive and 41/43 (95%) non-ovarian carcinoma cases were negative. The 2 non-ovarian carcinoma cases positive for PAX8 were renal cell carcinoma. The sensitivity and specificity of PAX8 was 96% and 95%, respectively.
Conclusions: The histologic distinction of EOC/PC from its mimics is clinically important yet not one single stain has been proven to be highly reliable. Our data clearly showed that PAX8 is very highly sensitive and specific in primary EOC/PC, especially on biopsy and cytology on cell blocks. Therefore, we highly recommend adding it to the immunohistochemical panel for the diagnosis of EOC/PC, especially in institutions where neoadjuvant is gaining popularity.
Category: Gynecologic & Obstetrics

Monday, March 19, 2012 9:30 AM

Poster Session I Stowell-Orbison/Surgical Pathology/Autopsy Awards Poster Session # 187, Monday Morning


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