[1088] PAX2, a Sensitive and Specific “Negative” Marker To Differentiate Diffuse Malignant Mesotheliomas of Peritoneum from Serous Carcinomas of Müllerian Origin

FF Gao, AM Krasinskas, M Chivukula. University of Pittsburgh Medical Center, Pittsburgh, PA; Magee-Women's Hospital, University of Pittsburgh Medical Center, Pittsburgh, PA

Background: Mesotheliomas are rare neoplasms of serosal surfaces (pleura followed by the peritoneum, pericardium and tunica vaginalis of testis). Peritoneal mesotheliomas (PM) accounts for 10% of all mesotheliomas and are often disseminated in the peritoneal cavity as multiple nodules including localized masses in the ovaries that are clinically and histologically similar to serous adenocarcinomas of müllerian origin. It is important to differentiate these tumors given their diverse responses to the chemotherapy and/or radiotherapy. Several immunohistochemistry markers including calretinin and Wilm's tumor gene 1 (WT-1) are used in combination as positive/negative markers in a panel in distinguishing these tumors. PAX2 gene encodes a transcription factor and it was recently demonstrated in benign epithelial cells of the female genital tract as well as serous carcinomas of müllerian origin. The aim of our study is to determine the sensitivity/specificity of PAX 2 in definitely differentiating PM from serous carcinomas.
Design: Twenty-five (25) cases of PM were retrieved from our pathology case archives. The cases were represented on a single tissue microarray (TMA) with 3-fold redundancy (TMA-1). In comparison, forty-seven (47) cases of serous carcinomas of müllerian origin [fallopian tube (26), ovary (11), and peritoneum (10)] were retrieved. All cases were stained with rabbit polyclonal PAX2 antibody, WT-1 and calretinin. Only nuclear staining was considered positive for PAX 2 and WT-1. Cytoplasmic/nuclear staining is considered positive for calretinin.
Results: All PM were entirely negative for PAX2 (0%, 0/25) in contrast to 80% (38/47) of serous adenocarcinomas of müllerian origin expressed PAX2. WT-1 expression was seen in 92% (23/25) of PM and 100% (47/47) in serous carcinomas of müllerian origin. Calretinin positivity was seen in 88% (22/25) of PM while all serous carcinomas of müllerian origin were entirely negative (0%, 0/47).
Conclusions: Our results demonstrate that 1) PAX 2 is a “negative”marker for PM while Calretinin is a “negative” marker for serous carcinomas of müllerian origin. 2) Although other immunohistochemistry markers such as WT-1 are essential for making the diagnosis of PM or serous carcinomas of müllerian origin, the combination of PAX 2 and Calretinin is a valuable tool to differentiate this two histological similar diseases efficiently.
Category: Gynecologic & Obstetrics

Wednesday, March 24, 2010 1:00 PM

Poster Session VI # 178, Wednesday Afternoon


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