Malignant mesenchymoma is a rare soft tissue neoplasm containing two or more subtypes of sarcoma within the same tumor, not including fibrosarcoma or undifferentiated sarcoma. In case reports and a few small series these tumors have generally been associated with a poor prognosis. We report herein a case involving a 38-year-old man with a 25-cm, 3.75-kg, rapidly growing malignant mesenchymoma with distinct areas of chondrosarcoma, osteosarcoma, and myxoid liposarcoma in addition to fibrosarcoma. We performed a radical resection, including right hemicolectomy with primary ileocolic anastomosis and external iliac artery segmental resection with hypogastric artery transposition. Approximately 24 months after surgery the patient has no evidence of tumor recurrence or vascular insufficiency.
TECHNIQUEThe patient, a 38-year-old man, sought treatment for a painless, asymptomatic abdominal mass that seemed to have gotten larger since he first noticed it 2 months earlier.He had no other significant medical conditions. Physical examination revealed a football-sized, nontender, right-sided abdominal mass. There was no adenopathy or other associated findings. Abdominal computerized axial tomography (CT) showed a right-sided midabdominal mass measuring 23 by 19.5 by 15 cm (Fig. 1). The mass was heterogeneous, with areas of probable central necrosis and foci of calcification, and did not appear to involve the aorta, vena cava, right kidney, or ureter. No tissue plane was identified between the mass and the right iliacus muscle. The abdominal CT also suggested a 1.5-cm splenic nodule. A chest CT was also performed to rule out pulmonary metastases. Because the radiographic findings were highly suggestive of retroperitoneal sarcoma, we elected not to perform a percutaneous biopsy and chose to proceed directly to surgery.At laparotomy, a large, right retroperitoneal mass was present, displacing the right colon anteriorly. There was no evidence of metastatic disease and the splenic nodule suggested on the abdominal CT was not palpable. No tissue plane could be created between the mass and the right colon. Inferiorly, the tumor was adherent to the iliacus muscle and the external iliac artery. It did not involve the kidney or ureter. We performed an en bloc resection including the right colon, and 2.5 cm of the external iliac artery and iliacus muscle.Although the patient had received mechanical and antibiotic preoperative bowel preparation, we were reluctant to perform vascular reconstruction with prosthetic material in a potentially contaminated wound. Although an autogenous vein graft was considered, we elected to reconstruct the external iliac artery with a hypogastric artery transposition. After mobilizing the hypogastric artery and ligating multiple branches, we transected it distally and rotated it anteriorly to the distal external iliac artery (Fig. 2). A spatulated end-to-end anastomosis was performed with running 5-0 polypropylene. After restoring perfusion to the right leg, femoral and distal pulses were present. A primary...