Undifferentiated pleomorphic sarcoma of the small intestine presenting with intussusception in a patient with prior well-differentiated liposarcoma.

An 88-year-old man presented with abdominal pain and vomiting. Contrast-enhanced computed tomography revealed a target sign, suggesting intussusception caused by a small-bowel tumor. Laparoscopic exploration was performed, followed by manual reduction using the Hutchinson technique and segmental small-bowel resection. Histopathological examination revealed a 3-cm submucosal tumor composed of pleomorphic tumor cells. Immunohistochemistry showed no specific lineage differentiation, and staining for MDM2 and CDK4 was negative. Because of his history of well-differentiated liposarcoma, metastatic disease, and dedifferentiated liposarcoma were considered. However, re-evaluation of the previous specimen showed no histological similarity to the present tumor, and the tumor was diagnosed as primary undifferentiated pleomorphic sarcoma of the small intestine. The postoperative course was uneventful, with no evidence of recurrence at the 2-year follow-up. Histological and immunohistochemical comparison is important in patients with a history of well-differentiated liposarcoma.