GATA4 is diagnostically useful for distinguishing primary ovarian mucinous carcinomas from metastatic colorectal adenocarcinomas to the ovary.

Aim: Determining the primary origin of an ovarian mucin-producing carcinoma can be challenging at times because some metastases of primary colorectal origin may exhibit gross, microscopic, and/or immunohistochemical features that overlap with those of primary ovarian mucinous carcinomas (OMCs). We hypothesized that GATA binding protein 4 (GATA4) might be a novel, useful marker for differentiating primary OMCs from metastatic colorectal adenocarcinomas to the ovary.

Methodology: For comparison with the usefulness of other markers (special AT-rich sequence-binding protein 2 (SATB2) and caudal type homeobox 2 (CDX2)), we elucidated the expression profiles of GATA4 in OMCs, colorectal non-mucinous adenocarcinomas (CNMACs), and colorectal mucinous adenocarcinomas (CMACs) using immunohistochemistry.

Results: We confirmed GATA4 expression (H-score ≥50 points) in 93%, SATB2 in 0%, and CDX2 in 64% of 14 OMCs. GATA4 was expressed in 13%, SATB2 in 90%, and CDX2 in 93% of 30 CNMACs. GATA4 was expressed in 20%, SATB2 in 73%, and CDX2 in 100% of 30 CMACs.

Conclusion: The expression of GATA4 in a mucus-producing ovarian tumor strongly supports it being a primary OMC rather than a metastatic colorectal carcinoma: GATA4 expression indicates OMC and SATB2 expression indicates colorectal adenocarcinoma. However, three cases of colorectal adenocarcinoma were GATA4-positive and SATB2-negative, so the GATA4/SATB2 marker combination is not absolute for determining the primary site. Further research for more markers is necessary to find the ideal combination.