Development of port-site metastasis after pneumoperitoneum - A scanning electron microscopy study

Background: Port-site metastasis is a critical problem in laparoscopic cancer surgery, the pathogenesis and means of prevention are still unclear. The aim of this study was to clarify by scanning electron microscopy the initial morphologic changes in the development of portsite metastasis. Methods: Fifteen nude mice were injected with human gastric cancer (MKN 45) cells. Mice were killed on days 0, 3, and 8 (n = 5 each day) after intraperitoneal injection of 5 x 105 cancer cells and carbon dioxide (CO2,) pneumoperitoneum at 4-6 mmHg for 20 min, The abdominal wall with the port sites was harvested and examined under both light and scanning electron microscopy. Results: Immediately after CO2 pneumoperitoneum (day 0), the abdominal peritoneum was peeled away and the muscular layer was destroyed at the port site in all mice. Several cancer cells were attached to the injured port sites. On day 3, the subperitoneal tissue and muscular layer defects were replaced by granulation tissue, and several cancer cells were observed in the subperitoneal tissue. On day 8, a small nodule was macroscopically visible at the port sited it was completely covered by mesothelial cells and consisted of numerous cancer cells. Conclusions: Free cancer cells appear to attach to the injured port sites immediately after CO2 pneumoperitoneum, and these are associated with the development of port-site metastasis after laparoscopic cancer surgery.