[407] Diagnostic Utility of MIB-1 and p53 in Separating Metastatic Carcinoma of Gynecologic Origin from Benign Epithelial Lesions in Pelvic Washing Cytology Specimens

Shweta Patel, Jacqueline Nunez, Alok Mohanty, Jan F Silverman, Yulin Liu. Allegheny General Hospital, Pittsburgh, PA

Background: Benign reactive conditions such as endosalpingiosis in female peritoneal washings can oftentimes be a diagnostic challenge. Misdiagnosing benign conditions as carcinoma, especially in patients with known ovarian or endometrial carcinoma, can have disastrous implications. Several studies have proposed an immunohistochemical (IHC) profile on these atypical cells but they only demonstrate whether the cells are of epithelial or mesothelial origin. The question still remains whether the cells are reactive or malignant. In this study, we evaluated the utility of p53 and MIB-1 to distinguish reactive endosalpingiosis from metastatic carcinoma under the hypothesis that the reactive condition should have very low proliferative index and lack expression of p53, while metastatic carcinoma might be immunohistochemically positive for p53.
Design: Thirty-seven peritoneal cytology cases including 22 cases of endosalpingiosis and 15 cases of metastatic carcinomas of gynecologic origin were retrieved from our database. Surgical resections of 5 benign fallopian tubes served as negative control. Immunoreactivity for p53 was scored in a four-tiered manner with positive results defined as scores of 1 (<25% cells staining with minimal intensity), 2 (moderately intense staining in 25-50% of cells) and 3 (strong staining in >50% of cells). MIB-1 proliferation index was calculated by counting the number of positive cells in 5 separate high power fields.
Results:

MIB-1 and p53 Reactivity in endosalpingiosis and metastatic carcinoma
 MIB-1p53
Endosalpingiosis2%0% (0/22)
Metastatic carcinoma of gynecologic origin17%60% (9/15)
Benign fallopian tube0%0% (0/5)


None of our endosalpingiosis cases stained for p53, while 60% of metastatic carcinomas showed diffuse and strong positivity for p53 (P < 0.001, chi2 test). The average MIB-1 count for endosalpingiosis and metastatic carcinoma were 2% and 17%, respectively.
Conclusions: Our results indicated that benign epithelial lesions in peritoneal fluid cytology show low proliferative index and lack p53 expression, while metastatic carcinomas show much higher proliferative index and strong p53 expression. We suggest a panel of MIB-1 and p53 can be very useful in distinguishing benign reactive endosalpingiosis from metastatic carcinoma in pelvic washings, especially in patients with a prior history of uterine or ovarian carcinoma.
Category: Cytopathology

Monday, March 4, 2013 1:00 PM

Poster Session II # 85, Monday Afternoon

 

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