RESUMO
Background: The pathological differential diagnosis between primary and metastatic ovarian malignant tumors is usually difficult, specially for tumors originating in the gastrointestinal system or breast. Aim: To define an immunohistochemical flow chart to discriminate these tumor types. Material and methods: We performed a immunostaining analysis using a panel of six antibodies (CK 7, CA 125, CEA, CK20, BRST-2 and CA 15-3) in 3 tumor groups: 11 ovarian, 14 breast and 12 colonic primary tumors and in a study group of 38 ovarian tumors whose primary origin was unknown. Results: We defined an ovarian immunohistochemical pattern (CEA-/CK20-, 45 percent in ovarian tumors, 0 percent in breast or colonic tumors, p <0.001); an ovary/breast pattern (CEA+/CK20-, 0 percent in colonic tumors, p <0.001): a breast pattern (CEA+/CK20-/BKST-2+, 64 percent in breast tumors and 0 percent in colonic and ovarian tumors, p <0.001) and a colonic pattern (CEA+/ CK20+/CK7-, 67 percent in colonic tumors and 0 percent in breast and ovarian tumors, p <0.001). Conclusions: Employing a simple panel of antibodies, characteristic immunohistochemical patterns were defined for ovarian, breast and colonic tumors. These patterns allowed the identification of the origin of most tumors of the study group