[Experimental study of the mechanism of peritoneal dissemination--with special reference to scanning electron...

Most malignant ovarian tumors metastasize by peritoneal dissemination and have a poor prognosis. Few studies have been made to determine how free ovarian tumor cells act on the peritoneum and become lodged and proliferate therein and much still remains to be clarified concerning this issue. In the present study, we transplanted 2 X 10(6) cells of JOHYL-1 strain established from an atypical dysgerminoma into the peritoneal cavity of nude mice observed serially morphological changes in the peritoneum resulting from tumor cell dissemination both by light microscopy and SEM. The findings thus obtained may be summarized as follows: From 5 to 7 days after intraperitoneal transplantation of tumor cells, mesothelial cells of the peritoneum began to swell, with the intercellular boundaries becoming distinct. Microvilli of the mesothelial cells increased in number, forming a mesh-like structure, and in some places were found to be in direct contact with a tumor cell. From 10 days after tumor cell transplantation onwards the mesothelium showed enlarged intercellular spaces in some places, and at these sites tumor cells were seen to have adhered. On other sites mesothelial cells were being partially lost. From 11 days after being transplanted, the tumor cells started proliferating and infiltrating in the muscle layer. Concerning the site of tumor cell implantation, evidence was obtained showing that tumor cells adhered to intercellular spaces of mesothelial cells, and/or in defects formed on connective tissue by a loss of mesothelial cells. The study thus demonstrated a salient usefulness of the JOHYL-1 ascites type cell line, with a reliably great capacity for growth in vivo, as an experimental model for the study of peritoneal dissemination of tumor cells.