We assessed the value of cytokeratin 17 (CK17) expression for the differential diagnosis between primary ovarian mucinous tumors and metastases from the gastrointestinal tract (GIT) and the significance of CK17 expression in a broad spectrum of primary ovarian tumors with respect to their prognosis. The sample set consisted of 554 primary ovarian tumors and 255 GIT tumors. In the primary ovarian tumors, a higher CK17 expression (in > 10% of tumors cells) was present only in 0-11.