Synchronous Presentation of Intraperitoneal and Retroperitoneal Dedifferentiated Liposarcoma: A Case Report.

Liposarcomas (LPS) are a group of tumors with different subtypes, some of which are more aggressive. They most often arise in the retroperitoneum, while occurrence within the peritoneal cavity is uncommon. Symptoms are usually nonspecific. We report the case of a combined intraperitoneal and retroperitoneal dedifferentiated LPS (DDLPS), which presented significant diagnostic and therapeutic challenges. We report the case of a 63-year-old woman with a history of recurrent retroperitoneal LPS, who presented to our department with right hypochondriac discomfort and progressive abdominal distention. Clinical and imaging examinations revealed bilateral masses: a left intraperitoneal mass and a right retroperitoneal mass. The patient underwent cytoreductive surgery involving the resection of the intraperitoneal mass, while the retroperitoneal tumor was deemed unresectable due to the invasion of the inferior vena cava. Histopathological analysis confirmed the diagnosis of DDLPS. Follow-up examinations showed a stable clinical condition. Due to the rarity of intraperitoneal DDLPS, this case contributes valuable data to help improve understanding and support the development of standardized guidelines for its management. Additionally, it illustrates the challenges of treating complex recurrent retroperitoneal LPS and underscores the critical role of molecular murine double minute 2 (MDM2) analysis in diagnosis.