Gastrointestinal: A retroperitoneal liposarcoma that formed a fistula into the descending colon

Abstract

Liposarcoma frequently occurs in the retroperitoneum and lower extremities, accounting for 9.8–16% of all soft tissue sarcomas. Liposaromas vary by histology and can be classified into four types. Those four types are well differentiated, myxoid/round cell, pleomorphic and dedifferentiated. This classification corresponds to the clinical aspect and prognosis of patients. Dedifferentiated liposarcoma (DDL) has both a well differentiated liposarcoma and a high grade nonlipogenic sarcoma within the tumor. It is difficult to diagnose DDL histologically. DDL can show a variety of histological appearances. The most common phenotype is malignant fibrous histiocytoma. Other phenotypes include leiomyosarcoma, osteosarcoma, rhabdomyosarcoma, and angiosarcoma. For DDL, prognosis is generally poor compared with the other types of liposarcoma. It shows high recurrence rate of 40-83%, metastasis rate of 15–30%, and the overall 5-year survival rate of 20%. DDLs often originate in the retroperitoneum, extremities, trunk, testis, and spermatic cord. A 61-year-old man was admitted to our hospital with 38.8°C of fever and general weakness. He had a history of a 20 × 10 cm well-differentiated retroperitoneal liposarcoma and underwent debulking surgery and intraoperative radiotherapy eight years previously. After surgery, there was no remnant mass visible on the abdominal computed tomography (CT) scan. On the current admission, physical examination revealed a palpable mass in the left mid abdomen. CT scan revealed a 8.5 × 8.3 cm sized large mass abutting the descending colon and left kidney in the left retroperitoneal cavity. The tumor encased a segment of the bowel loop and there was air density suspicious of tumor fistulization into the colonic lumen. Colonoscopy showed a fistula into the descending colon 30 cm from the anal verge (Figure 1). A yellowish mass was seen through the fistula with erythematous and edematous mucosal changes around the fistula. We suspected that the liposarcoma had recurred, and the patient underwent left colon segmental resection. The specimen showed a 9.5 × 8.5 cm sized, well-demarcated, yellowish-gray, lobulated, glistening, and firm mass. Microscopic findings showed a dedifferentiated liposarcoma containing a well-differentiated component with fat lobules and a nonlipogenic hypercellular area. There were scattered atypical lipocytes (Figure 2, upper panel) and pleomorphic spindle cells (Figure 2, lower panel, H&E, orig. mag. ×200) consistent with a subtype of malignant fibrous histiocytoma. Contributed by