1. ¹Emory University School of Medicine, Atlanta, GA, USA
2. ²The James Homer Wright Pathology Laboratories, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA

Correspondence: Dr S Logani, MD, Department of Pathology, Emory University Hospital Suite H187, 1364 Clifton Road, NE, Atlanta, GA 30322, USA. E-mail: slogani@emory.edu

Received 16 June 2004; Revised 16 July 2004; Accepted 16 July 2004; Published online 24 September 2004.

Abstract

Distinguishing primary ovarian carcinoma, particularly endometrioid and mucinous subtypes, from metastatic colorectal carcinoma to the ovary is often difficult on histologic examination alone. Recently, three immunohistochemical markers CDX2, a homeobox gene encoding an intestine-specific transcription factor; -methylacyl-CoA racemase (AMACR/P504S), a mitochondrial and peroxisomal enzyme with fairly restricted expression in selective tumors and -catenin, an adenomatous polyposis coli (APC) mutation product resulting in activation of the Wnt pathway, have been reported to have specific and sensitive expression in colorectal carcinomas. We evaluated a panel consisting of antibodies to CDX2, -catenin and P504S in 23 primary ovarian adenocarcinomas (13 mucinous and 10 endometrioid) and compared the findings to 22 metastatic colorectal adenocarcinomas (seven mucinous and 15 nonmucinous tumors with endometrioid-like morphology hereafter referred to as pseudo-endometrioid) to the ovary stained with the same panel. Twenty (91%) metastatic tumors expressed at least two markers and seven (32%) expressed all three. In contrast, only three (13%) primary ovarian tumors expressed at least two markers and none expressed all three. Strong (2+, 3+) and diffuse (>40%) expression for CDX2 was noted in 21 (95%) metastatic tumors and five (22%) primary ovarian tumors (three mucinous, two endometrioid). P504S was similarly expressed in seven (32%) metastatic and none of the primary ovarian carcinomas. Nuclear expression of -catenin was noted in 13 (59%) metastatic tumors and in eight cases (36%), it was diffuse and strong. In contrast, four (19%) primary tumors showed nuclear expression of this protein with only one (5%) case expressing it in a diffuse pattern. Immunohistochemical expression of gene products and enzymes of colorectal carcinogenesis in some primary ovarian carcinomas suggest that the morphologic similarities between colorectal and mucinous/endometrioid carcinoma of the ovary extends to the genetic level, although differences in the level of expression exist between these tumors. Diffuse expression of all three markers (CDX2, -catenin and P504S) in a tumor in the ovary was found to be virtually diagnostic of metastasis from a colorectal primary in this study.