Giant retroperitoneal dedifferentiated liposarcoma with intraperitoneal extension: A case report.

Retroperitoneal liposarcoma is a rare malignant mesenchymal neoplasm of adipocytic origin that often remains clinically silent until it reaches a considerable size. We report the case of a 66-year-old woman presenting with progressive right lower abdominal pain and a palpable abdominal mass. Initial ultrasonography demonstrated a large heterogeneous subhepatic mass containing both macroscopic fat and solid components with cystic areas. Contrast-enhanced CT and multiparametric MRI further characterized the lesion, revealing a giant retroperitoneal mass with secondary intraperitoneal extension, abundant macroscopic fat, a large enhancing nonlipomatous component, thick septa, necrotic areas, and diffusion restriction, findings highly suggestive of dedifferentiated liposarcoma. Histopathological confirmation was obtained by image-guided core needle biopsy. Owing to the extensive local disease and close relationship with major abdominal vessels, the lesion was initially considered unresectable, and the patient was referred to the multidisciplinary sarcoma team for systemic chemotherapy. We report the case of a giant dedifferentiated retroperitoneal liposarcoma in a 66-year-old woman which highlights the pivotal role of multimodality imaging in the characterization of giant retroperitoneal liposarcomas, enabling accurate preoperative diagnosis, biopsy guidance, and therapeutic planning.