Mucinous tumors of the vermiform appendix and ovary, and pseudomyxoma peritonei: histogenetic implications of cytokeratin 7 expression.

Cytokeratin 7 (CK-7) has been shown to be uncommonly expressed in colonic epithelial tumors, as opposed to ovarian epithelial tumors, which are always CK-7 positive. The authors investigated the expression of CK-7 in 17 appendiceal cystadenomas and carcinomas, 20 mucinous borderline tumors of the ovary, 10 cases of simultaneous mucinous tumors of the appendix and ovary, three so-called high-stage mucinous borderline tumors of the ovary, and three cases of pseudomyxoma peritonei (PP) of unknown origin. Nine appendiceal cystadenomas were CK-7 negative; two of these were associated with PP, and the peritoneal lesions were negative as well. Three cystadenomas were CK-7 positive. Three appendiceal carcinomas were CK-7 negative, and in one case the metastases were also negative. Two carcinomas were CK-7 positive. All 20 ovarian borderline tumors were CK-7 positive. Six cases of simultaneous mucinous tumors of the ovary and appendix were CK-7 negative, as were their peritoneal mucinous deposits. Four cases showed a positive reaction in both appendiceal and ovarian sites. Two of three so-called high-stage ovarian borderline tumors were CK-7 negative. All three cases of PP of unknown origin were CK-7 negative. In conclusion, appendiceal cystadenomas are often CK-7 negative, whereas ovarian mucinous borderline tumors are always CK-7 positive. The concordant staining pattern for CK-7 of simultaneous mucinous tumors involving the appendix and ovary (60% of which were CK-7 negative) supports an appendiceal origin for these tumors. Our results also support an appendiceal (or colonic) source for any CK-7-negative mucinous tumor involving the ovary or the peritoneum. Furthermore, our findings are in agreement with the assumption that mucinous borderline-like tumors in the ovary associated with PP are not ovarian in origin but are often, if not always, metastatic from an appendiceal (or other) mucinous tumor.