[783] Microfibrillar Associated Protein 5 (MFAP 5): A Marker for Desmoplasia That Facilitates the Distinction between an Invasive Component and Pseudoinvasion in Colonic Adenomas

Lei Zhao, Tatjana Antic, Shu-Yuan Xiao, Charles VanSlambrouck, John Hart. University of Chicago, Chicago, IL

Background: Distinction between invasive adenocarcinoma and submucosal displacement of adenomatous mucosa in colonic polyps can be problematic in clinical practice. Recent microarray studies have demonstrated that tumor stroma exhibits reproducible gene-expression changes compared to normal stromal tissue. MFAP5, a 25-kD glycoprotein that is involved in elastic microfibril assembly, has been demonstrated to be significantly down regulated in tumorous stroma [Jia et al. Cancer Res 2011]. The aim of this study is to confirm the reduced expression of MFAP5 in tumor stroma by immunohistochemistry and evaluate the utility of MFAP5 as a diagnostic marker.
Design: An immunohistochemical stain for MFAP 5 (Sigma) was first performed on ten invasive colon cancer resection specimens to compare the its expression pattern in invasive tumor and in the surrounding lamina propria and submucosa. Then a total of 24 diagnostically challenging adenomatous polypectomy specimens (6 with an invasive focus and 18 with pseudoinvasion) were used to evaluate the diagnostic value of MFAP5.
Results: In all 10 colon cancer resection cases there was no reactivity in the desmoplastic stroma surrounding the invasive component, while the uninvolved lamina propria and submucosa exhibited strong diffuse reactivity in stromal cells.

In 16 out of 18 polypectomy specimens with pseudoinvasion, strong reactivity was preserved in the stroma surrounding the displaced adenomatous mucosa (left panel of figure below). Lack of staining in the stroma surrounding small foci of invasive tumor was observed in all 6 malignant polyps (right panel of figure below).

Conclusions: MFAP5 is a useful marker to demonstrate tumor associated desmoplastic stromal proliferation. It facilitates the distinction between pseudoinvasion and true invasive cancer in colonic adenomatous polyps with high sensitivity and specificity.
Category: Gastrointestinal

Monday, March 4, 2013 9:30 AM

Poster Session I Stowell-Orbison/Surgical Pathology/Autopsy Awards Poster Session # 124, Monday Morning


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