Ten years ago, a seventy-year-old female underwent extirpation of a left retroperitoneal tumor that was 58×36 mm in size. The pathological diagnosis was malignant peripheral nerve sheath tumor (MPNST) at that time. The patients visited our hospital with the chief complaint of back pain at ten years after surgery. Computer tomography (CT) showed recurrent tumors at the pancreas and the left kidney. Fine-needle aspiration biopsy was performed because of the possibility of pancreatic tumor. The pathological diagnosis was the recurrence of MPNST. The patient underwent extirpation of the recurrent tumors along with the pancreatic body and tail, transverse colon, spleen and left kidney. The definitive diagnosis was dedifferentiated liposarcoma with murine double minute 2 (MDM2) gene amplification and positive of p16Ink4 (p16). The previously resected tumor also revealed MDM2 gene amplification and positive of p16. Based on these results, our diagnosis in this case was recurrence of dedifferentiated liposarcoma. At 6 months after surgery, the patient had no local recurrence or distant metastases.