[1200] DPEP1, a Useful Immunohistochemical Tool in Distinguishing Primary from Metastatic Endometrioid and Mucinous Ovarian Tumors

Elizabeth Marchetti, Asangi Kumarapeli, Wilfrido Mojica. State University of New York at Buffalo, Buffalo, NY

Background: Metastasis of colorectal adenocarcinoma (ADC) to the ovary is not an uncommon occurrence. In particular, mucinous and endometrioid ovarian ADC phenotypes have proven to be diagnostically challenging in the differential diagnosis with metastatic colon ADC. From recent proteonomic studies that demonstrated significant upregulation in colonic ADC relative to matched normal tissue, DiPeptidase-1 (DPEP1) has emerged as a potential diagnostic marker for colonic ADC. This finding has direct relevance to cases wherein the differential diagnosis predicament previously described are encountered, as DPEP1 may function to further help delineate metastatic colonic ADC from primary ovarian mucinous or endometrioid tumors.
Design: Four cases of mucinous colonic ADC and ten cases of conventional colonic ADC from female patients were retrieved from archival files as well as 4 cases of endometrioid ovarian tumors, 6 cases of endometrioid uterine tumors, and 4 cases of mucinous ovarian tumors. All sections were subjected to immunohistochemistry with antigen retrieval using an antibody to DPEP1 (Sigma) at a titer of 1 : 1500.
Results: The conventional colonic ADC demonstrate diffuse, strong expression for DPEP1 in a polarized (apical/luminal centric) fashion. The mucinous colonic ADC showed some cytoplasmic staining with patchy apical/luminal staining. All four mucinous ovarian tumors were negative. Half of the ovarian endometrioid tumors expressed DPEP1, but in a punctuate fashion, with a circumferential pattern on the positive cells. Only 1 of the 4 endometrial endometrioid ADC cases expressed DPEP1, and in a manner similar to the ovarian endometrioid tumors.
Conclusions: DPEP1 has utility in distinguishing colonic ADC from mucinous and endometrioid ADC of the ovary and is based on the presence of expression and the pattern of staining. The characteristic diffuse apical/luminal centric staining noted in the colonic ADC was only focal in the mucinous colonic ADCs, but still present in contrast to its complete absence in mucinous ovarian tumors. For those ovarian and endometrial tumors that did express DPEP1, the staining was focal and circumferential, in contrast to the apical/luminal staining pattern noted in colonic ADCs.
Category: Gynecologic & Obstetrics

Wednesday, March 21, 2012 9:30 AM

Poster Session V # 153, Wednesday Morning


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