[1071] Single Isolated Cells Showing Loss of E-Cadherin Expression in the Subtypes of Pseudomyxoma Peritonei; Its Possible Role in the Disease Progression.

Young Wha Koh, Hyung Kyung Kim, Bong Hee Park, Kyu-Rae Kim. University of Ulsan College of Medicine, Asan Medical Center, Seoul, Korea

Background: Pseudomyxoma peritonei (PMP) can be classified into two subtypes, disseminated adenomucinosis (DPAM), and peritoneal mucinous carcinomatosis (PMCA) according to the cytomorphologic features of peritoneal lesions and clinical behavior. However, differences in the mechanism of disease progression between the two subtypes have not been explained. We suspected that the difference in the expression of adhesion related protein or epithelial mesenchymal transition, which is crucial for invasion, might be related to the difference of progression rates and prognosis between the two subtypes.
Design: To compare the expression of adhesion related proteins, we performed immunohistochemical stainings for E-cadherin, vimentin, cytokeratin 7 and 20 between the two subtypes in the peritoneal lesions of PMPs using paraffin sections. The cases were 52 pseudomyxoma peritonei treated at Asan Medical Center during 1995-2010. We counted the number of cellular strips composed of cohesive cell clusters and single isolated cells (SICs) floating in mucin pools separately using 10x10 grid micrometer from Olympus BX51 at 400x magnification field on H&E stained and immunostained sections, and then compared the number of SICs with the expression patterns for E-cadherin, and vimentin in cellular strips and SICs, respectively between the two subtypes. CK7 and 20 were used for identification of tumor cells.
Results: Loss of E-cadherin expression was significantly higher in SICs compared to cohesive cellular strips in both subtypes. Median follow up periods was 998 days (range: 14-4631 days). According to the histologic subtypes and the number of SICs, significant difference in the overall survival rates was identified between the two subtypes. The patients having more than 30 SICs/x400 fields had signficantly worse prognosis compared to those having less than 30 SICs, and the number of cases showing more than 30 SICs was significantly higher in PMCA compared to DPAM (p<0.001). Vimentin expression was increased in the SICs, but vimentin expressing cells were undistinguishable from the macrophage in the mucin pools.
Conclusions: Slow rate of tumor progression in DPAM subtype of pseudomyxoma peritonei might be attributable to the smaller number of SICs showing loss of cell adhesion molecules, E-cadherin, whereas rapid progression of PMCAs subtype to the larger number of SICs showing loss of cell adhesion molecules.
Category: Gynecologic & Obstetrics

Tuesday, March 1, 2011 1:00 PM

Poster Session IV # 118, Tuesday Afternoon


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