A rare retroperitoneal tumor.

A 68 year old man was hospitalized for pulmonary embolism. A month ago, he had a myocardial infarction and 10 days ago he was treated surgically by triple coronary artery bypass grafting. His personal medical and surgical history includes hypertension, appendectomy for appendicitis 50 years ago and exploratory laparotomy for obstructive ileus due to adhesions 5 years ago. He has no family history for malignancy. Abdominal CT and MRI performed for causative evaluation of the pulmonary embolism, revealed a 5 cm large solid mass of the mesenteric root with clear smooth margins and inhomogeneous density. The mesenteric vessels were not infiltrated. The patient did not mention any gastroenterologic disorders (vomiting, blood loss and defacation problems) and had no abnormal signs on physical examination. The performed coloscopy was negative. The surgical specimen was a solid, hard, well defined retroperitoneal tumor lying in front of the superior mesenteric artery and the left renal vein [Figures 1 and 2].

Figure 1

Retroperitoneal lesion in MRI

Figure 2

The same lesion in CT

QUESTIONS

Q1. What is the most likely diagnosis?

Q2. Which are the manifestation forms of these entities?

Q3. Which are the main symptoms?

Q4. What is the treatment and prognosis?

ANSWERS

The frozen section showed a mesenchymal neoplasm with local cellularity that raised the question of differential diagnosis between mesenteric fibromatosis and gastrointestinal stromal tumor.[1] The histological report did not show nuclear atypia or necrosis. The immunohistochemical examination showed low cytoplasmic expression of c kit, no expression of CD34, S 100 or desmin and local expression of SMA. Ki 67 varied within tumor areas from 2% up to 6%. The findings were compatible with sporadic mesenteric fibromatosis (intra abdominal desmoid tumor).

Desmoid tumors are rare and unique mesenchymal neoplasms. They are well defined, local invasive tumors of fibrotic tissue with aggressive fibroblastic proliferation. They may occur as an abdominal wall mass, especially in young women during gestation or within a year of childbirth, as intra abdominal large mesenteric tumors or even as extremities masses in older people. Mesenteric fibromatosis accounts for <10% of sporadic desmoid tumors, while patiens with FAP have a 25% chance of developing a desmoid tumor. The development of this neoplasm has also been related to intra abdominal surgical operations, such as colectomies.

The symptoms and the complication of mesenteric fibromatosis may arise from compression or infiltration of adjacent organs and neurovascular structures. Epigastric discomfort and abdominal tenderness are the most common symptoms. Intestinal obstruction, ischemia and perforation, hydronephrosis and aortic rupture may occur, requiring immediate operative management.[2]

The treatment of mesenteric fibromatosis and desmoid tumors generally is the complete resection with a tumor -free margin. When the neoplasm cannot be totally removed, radiation in combination with resection is recommended. For the unresectable tumors radiation alone, tamoxifen, celecoxib, sulindac, interferon A or imatinib are further treatment options. Desmoid tumors behave as low-grade sarcomas, demonstrating high recurrence rates despite complete resection. When combined with FAP, the recurrence ranges from 60% to 80%.