Background: Local recurrence and peritoneal carcinosis may occur due to cells that have already been seeded at the time of the operation and may be not detected using conventional cytology. The aim of this study was to evaluate the presence of intraperitoneal free cancer cells in peritoneal washings of patients with colorectal carcinoma.
Methods: From January 2000 to October 2000, fifty-one patients who underwent surgical treatment for colorectal carcinoma were prospectively evaluated with peritoneal washings with cytologic examination prior to and following colon resection. Aspirated fluid from the abdominal cavity was centrifuged and subjected to cytological examination using Papanicolaou staining method. Immunohistochemistry for CEA and cytokeratin-20 was performed in cytological samples. These results were compared to clinicopathological data.
Results: The mean age was 63.1 years (range= 27 to 95 years) and 58.8% were women. The mean tumor size was 5.5 ± 2.3 cm, and they were located at the proximal rectum in 23.5%; left colon in 54.9% and right colon in 21.6%. Mucinous tumors were observed in 7.8% of patients, and the degree of differentiation was well differentiated in 13.7%, moderate in 76.5% and poorly in 7.8% tumors. The TNM classification included 0= 2%; I= 9.8%; II= 37.3%; III= 39.2% and IV= 11.8%. Intraperitoneal free cancer cells were detected in eight patients (15.7%), however macroscopic peritoneal dissemination was present in only one patient. 5/8 washings were positive in both, the conventional and immunohistochemical stainings. In two patients with suspected positive cytology, immunohistochemistry helped to confirm the presence of malignant cells. In one patient Papanicolaou staining was positive with negative immunohistochemistry. No patients converting negative to positive cytology during the procedure. There was no correlation between the presence of intraperitoneal free malignant cells and tumor size, levels of serum CEA, histology, degree of differentiation, invasion, and Duke's or TNM staging.
Conclusions: 1. Intraperitoneal free cancer cells are frequently detected in colorectal cancer; 2. Immunohistochemistry of the washings added sensitivity to cytologic examination in assessing patients with colorectal tumors. 3. Spillage of malignant cells in the peritoneal cavity after adequate surgical technique does not appear to occur.