False-negative peritoneal cytology in metastatic ovarian carcinoma

Seventy-nine laparotomies for disseminated intraperitoneal ovarian carcinoma were reviewed to determine the frequency and possible causes of false-negative peritoneal cytology. Negative peritoneal cytology (defined as any reading other than positive) was found in 16 of 79 cases (20%). False-negative cytology occurred more frequently with peritoneal washings (48%) than with ascites (6%; P less than .001); with second-look surgery (50%) than at primary surgery (12%; P = .004); with peritoneal metastasis less than 0.5 cm (50%) than with metastasis greater than 0.5 cm (16%; P = .02); and with bloody cytology specimens (25%) rather than specimens without blood (0%; P = .06). Volume of peritoneal specimen, architectural grade, cytologic grade, and stage of disease (III versus IV), did not affect the frequency of false-negative cytology. The high prevalence of negative cytology associated with peritoneal washings, small tumor size, and second-look surgery suggests that negative cytology is a result of poor distribution of peritoneal washings and infrequent exfoliation of malignant cells rather than misinterpretation of malignant cells present in cytology specimens.