Cytology of peritoneal washings in gynecologic patients. Diagnostic criteria and pitfalls

A total of 226 peritoneal washing specimens obtained from gynecologic patients over a three-year period was reviewed. The diagnostic problems encountered were: differentiating reactive mesothelium from low-grade malignancies; distinguishing between benign ovarian tumors, ovarian tumors of borderline malignancy and low-grade ovarian malignancies; and potential false-positive diagnoses in endometriosis. Low-grade malignancies could be distinguished from reactive mesothelium by evaluating subtle cytologic criteria and by comparing the cells to those of the tumor on histologic section. The differentiation of low-grade epithelial malignancies from benign epithelial lesions caused difficulties that could only be resolved by evaluating the histologic material. Positive peritoneal washings increased the stage in 8 of 110 patients undergoing initial surgery for gynecologic malignancy. Two of 76 patients undergoing a second-look laparotomy had positive washings without histologic evidence of tumor. These ten patients did less well than did those with similar histology but negative washing cytology, despite receiving additional therapy because of the cytologic findings.