[943] Guanylyl Cyclase C Is a Specific Marker for Differentiating Primary and Metastatic Ovarian Mucinous Neoplasms

A Bombonati, V Ciocca, JP Palazzo, S Schulz, SA Waldman. Thomas Jefferson University Hospital, Philadelphia, PA

Background: Distinguishing primary ovarian mucinous neoplasms from metastatic mucinous adenocarcinomas can be difficult. Guanylyl cyclase C (GCC) is a brush border membrane receptor for the endogenous peptides guanylin and uroguanylin, and the homologous diarrheagenic bacterial heat-stable enterotoxins that is selectively expressed by epithelial cells from the duodenum to the rectum, but not by normal epithelia of the stomach or esophagus, or normal extramucosal cells in humans. We evaluated GCC expression in primary ovarian mucinous neoplasms and in primary gastrointestinal adenocarcinomas with ovarian metastases to determine whether GCC could be used for differentiating primary and metastatic ovarian mucinous neoplasms.
Design: A total of 48 ovarian tumors were studied: 27 primary ovarian mucinous neoplasms (7 cystadenomas, 10 borderline tumors, and 10 cystadenocarcinomas) and 21 metastatic mucinous adenocarcinomas (12 colorectal adenocarcinomas, 4 gastric signet-ring cell carcinomas, and 5 appendiceal mucinous tumors including 3 adenocarcinomas and 2 cystadenomas). Immunostains for GCC were performed using formalin-fixed paraffin-embedded tissue. Tumors were scored as follows: negative (no staining in any tumor cells); focal positivity (staining in <5 % of tumor cells); diffuse positivity (staining in > 5% of tumor cells). Only cells exhibiting distinct apical membrane staining, independently of the level of expression, were considered positive for GCC expression. In contrast, cytoplasmic staining was not considered positive staining.
Results: For primary ovarian mucinous neoplasms, 25 of 27 were negative for GCC. Diffuse positive staining for GCC (in both primary and metastatic tumors) was seen in 12/12 colorectal adenocarcinomas, 3/3 appendiceal mucinous adenocarcinomas, and 2/2 appendiceal mucinous cystadenomas. Of 4 cases of gastric adenocarcinoma with ovarian involvement, only 1 (primary tumor) exhibited focal GCC staining.
Conclusions: GCC may be a useful marker for differentiating primary and secondary ovarian mucinous neoplasms.
Category: Gynecologic

Wednesday, March 11, 2009 9:30 AM

Poster Session V # 148, Wednesday Morning