Metastatic pattern of CC531 colon carcinoma cells in the abdominal cavity:an experimental model of peritoneal carcinomatosis in rats

Background: Peritoneal spread of tumour cells is a major source of morbidit y and mortality in patients with colorectal cancer. In order to develop str ategies to prevent intraperitoneal dissemination and to treat peritoneal ca rcinomatosis, the spread of tumour cells in the peritoneal cavity was studi ed. Methods: Two million CC531 colon carcinoma cells were administered intraper itoneally in five groups of eight rats. The rats were killed after 1, 2, 4 and 8 hours and 3, 7, 14 and 21 days. After inspection of the abdominal cav ity, samples of blood and ascites were taken. Liver, spleen, omentum, mesen tery, diaphragm, parathymic lymph nodes and lungs were removed for histolog y and immunohistochemistry. Results: No abnormalities were seen in the abdominal cavity until day 3. Su bsequently the peritoneum and omentum became thickened and after 21 days al l rats had haemorrhagic ascites and peritoneal carcinomatosis. The abdomina l fluid contained tumour cells at all stages. The number of tumour cells de creased in the first 8 hours, and increased thereafter. At microscopy the p eritoneum was completely covered by tumour cells after 3 days. Tumour I cel ls concentrated in the milky spots (MS) of the omentum within 4 hours. The size of the MS increased as a result of an increase in number of tumour cel ls and macrophages. After 7-21 days the MS were completely replaced by tumo ur cells and new MS were formed. In the diaphragm tumour cells invaded the lymphatic lacunae after 8 h, and obliterated these after 3-7 days. Also inv asion of the muscle fibres was seen after 3 days. Microscopically no tumour cells were found in blood, liver, spleen, parathymic nodes and lung. Conclusion: After intraperitoneal administration of CC531 colon carcinoma c ells, tumour cells spread throughout the abdominal cavity, and concentrate in the milky spots of the greater omentum, the paracolic gutters, the subhe patic and subphrenic spaces and in the lymphatic lacunae of the diaphragm. (C) 2001 Harcourt Publishers Ltd.