Although ascites cytology is important for therapeutic strategies, it is difficult to distinguish cancer infiltration from reactive mesothelial proliferation in some patients. In this study, the authors applied CDX2 immunocytochemistry to improve diagnostic accuracy.
The authors examined the distribution of CDX2 expression in carcinoma specimens using paraffin-embedded tissues from various organs from 549 cancer patients. CDX2 immunostaining was applied to the 116 ascites specimens.
CDX2 expression was detected in a restricted range of cancers, with the vast majority of them originating from the gastrointestinal tract and pancreas. When applied to ascites specimens, no positive reactions were detected in any of the 81 cytology-negative and molecular genetic analysis-negative specimens. By contrast, 28 of 35 specimens diagnosed as suspicious for malignancy or malignancy showed a positive reaction. Furthermore, the authors found that a nuclear-positive reaction was easily evaluated, even with a high level of background staining, and single cancer cells in 10(6) normal cells could be detected.
Results suggest that CDX2 is a specific and sensitive marker to detect gastrointestinal and pancreatic malignancies in ascites cytology.