Flow cytometry. A new technique in the diagnosis of malignant ascites.

The diagnosis of peritoneal carcinomatosis is often dependent on the finding of malignant cells in ascitic fluid analysis by a trained cytologist. Other methods are needed to increase the current diagnostic yield of 60-90%. Abnormal DNA content is characteristic of most malignancies. In an attempt to detect aneuploidy, we used high-resolution DNA histogram analysis with fluorescent DNA-specific stains and flow cytometry to evaluate 33 ascitic fluid samples. Of 13 patients with malignant ascites, aneuploidy was demonstrated in 10. Six patients with proven peritoneal carcinomatosis and normal cytologic examination had abnormal DNA histograms. DNA quantitation and cytologic examination agreed in 24 of 33 cases. These findings suggest that flow cytometry is a rapid and useful technique in the diagnosis of malignant ascites. The presence of aneuploidy in cells from ascitic fluid is highly suspicious for peritoneal carcinomatosis and suggests the need for further evaluation for malignancy.