We examined the prognostic value of free malignant cells in the peritoneal cavity of patients with colon adenocarcinoma. In 1996-1999, 88 patients underwent peritoneal washing with cytologic analysis immediately before elective colon resection for adenocarcinoma with no evidence of peritoneal metastases. Peritoneal washing fluid was collected before abdominal exploration centrifuged immediately and stained with the May-Grünwald-Giemsa and Harris-Shorr methods. Malignancy was defined as recommended by Papanicolaou. Free malignant cells in peritoneal fluid were found in 25 of 88 (28%) patients (Dukes A 0, of 11, Dukes B 10 of 31, Dukes C 11 of 37, Dukes D 4 of 9). The positive rate was 24 of 75 (32%) among patients with tumors involving the serous layer and 1 of 13 (8%) among the others (p = 0.00989). Positive peritoneal washing was not significantly associated with survival in multivariate analysis.
Conclusion: The presence of free malignant cells in the peritoneal cavity of patients with colon cancer provided no further prognostic information relative to the Dukes classification in this study. The 5 years survival rates were 48% among patients with positive and negative peritoneal washing respectively (p = 0.09).