[A Case of Retroperitoneal Liposarcoma That Invaded and Filled the Jejunal Lumen].

A jejunal tumor was found with computed tomography in a 79-year-old man with a history of gastrectomy reconstructed with Billroth II method for gastric ulcers. The tumor with contrast effect extended into the afferent loop and invaded the retroperitoneum in the dorsal side. The tumor occupied the jejunal lumen in endoscopic examination. Malignant spindle cells were found in the biopsy specimen. An increase of MDM2 and CDK4 signals were observed in fluorescence in situ hybridization( FISH). Given the preoperative diagnosis of jejunal liposarcoma, we performed a resection of the tumor with partial jejunectomy and partial gastrectomy. In the pathological examination of the surgical specimen, the majority of the tumor was dedifferentiated sarcoma; relatively highly differentiated sarcoma cells were observed in the retroperitoneal lesion. Therefore, it was suspected that the retroperitoneal-derived liposarcoma had invaded the jejunal lumen.