Distinguishing primary mucinous
ovarian cancers from ovarian
metastases of digestive organ
cancers is often challenging.
Dipeptidase 1 was selected as the candidate novel marker of
colorectal cancer based on an analysis of a gene expression microarray. Immunohistochemical analysis indicated that 13/16 ovarian
metastases of
colorectal cancers, but only 1/58 primary mucinous
ovarian cancers, were
dipeptidase 1-positive (threshold; ≧25% expression, P<0.0001). Next, five immunohistochemical markers (
dipeptidase 1,
estrogen receptor-α,
cytokeratin 7,
cytokeratin 20, and caudal type homeobox 2) were analyzed in combination. In a hierarchical clustering analysis, the mutually exclusive expression of
cytokeratin 7 and
dipeptidase 1 specifically identified the ovarian
metastases of
colorectal cancers (P<0.0001). In a decision tree analysis,
cytokeratin 7, caudal type homeobox 2, and
dipeptidase 1 classified primary mucinous
ovarian cancers and ovarian
metastases of digestive organ
cancers with 90% accuracy. Finally, the five immunohistochemical markers were combined with six preoperative factors (patient's age,
tumor size, laterality, serum CEA, CA19-9, and CA125) and combinations were analyzed. Of the 11 factors, 4 (
dipeptidase 1,
cytokeratin 7, caudal type homeobox 2, and
tumor size) were used to generate a decision tree to classify primary mucinous
ovarian cancers and
metastases of digestive organ
cancers with 93% accuracy. In conclusion, we identified a novel immunohistochemical marker,
dipeptidase 1, to distinguish primary mucinous
ovarian cancers from ovarian
metastasis of
colorectal cancers. The algorithm using immunohistochemical and clinical factors to distinguish
metastases of digestive organ
cancers from primary mucinous
ovarian cancers will be useful to establish a protocol for the diagnosis of ovarian
metastasis.