The incidence of abdominal pregnancy is very rare, long-retained abdominal pregnancy undergoing fetal death and evolving to a lithopaedion is even more scarce. The authors report the case of a 60-year-old woman who discovered an abdominal mass 31 years ago that was recently identified intraoperatively as lithopaedion. Although imaging had revealed a low-level echogenic mass in the cavity, nobody had considered the possibility of a lithopaedion before the operation. The authors strongly suggest identifying the small skeletal frame through imaging that will be a very important preoperative sign that will lead to a diagnosis, otherwise neglected in the past years.