Foam cell formation is a very common pathologic finding in atherosclerosis, often found in some major organs. However, the involvement of the retroperitoneal organs is very rare and foam cell formation associated with borderline ovarian tumor has not been reported. Borderline ovarian tumors are epithelial ovarian tumors with a low growth rate, low potential to invade or metastasize, and excellent prognosis. Still, a rapidly growing borderline ovarian tumor can exert pressure on the retroperitoneal organs. It may cause retroperitoneal irritation and inflammation, and form a mass lesion in adjacent organs. We report the case of a 41-year-old woman with a borderline ovarian tumor and foam cell infiltration.