Malignant fibrous histiocytoma is the most common soft tissue sarcoma, and this generally occurs in 50-70-year-old people, but it can occur in a young adults [2
The most common symptom is a painless mass, and the patients with this tumor mainly complain about fatigue, weight loss and abdominal pain and specifically in the cases of abdominal and retroperitoneal malignant fibrous histiocytoma, and this can lead to hematuria, lower extremity pain, abdominal distension, varicose veins and hernia. Another recent case report described a patient with an iliopsoas compartment tumor the patient presented with pain in the ipsilateral groin and testicular regions [3
Our patient was managed without any symptoms for approximately 16 months after performing resection and then he complained of left lower abdominal pain as the hypertrophy of the mass accelerated at 18 months after surgery. We think the symptoms were mild when the tumor was small, but the symptoms were aggravated due to the increase in abdominal pressure as the tumor size increased.
Malignant fibrous histiocytoma generally refers to the group of tumors that originate from histiocytes, and making the specific diagnosis is difficult since these lesions have a variety of pathological types. Malignant fibrous histiocytoma usually consists of three types of cells: spindle shaped cells, round cells and giant cells. The pathologic findings greatly vary and it can be classified into five types depending on the distribution of these cells: the storiform-pleomorphic type, the myxoid type, the giant cell type, the inflammatory cell type and the angiomatoid type. Of these types, the storiform-pleomorphic type is most common and it accounts for approximately 65% of malignant fibrous histiocytomas [4
For the cases of malignant fibrous histiocytoma, it has been reported that they show pathologic findings different from the primary tumor, or other histologically very different tumors can occur for about 10% of them [5
For making the diagnosis, the clinical symptoms, the physical examination findings such as an abdominal mass and abdominal tenderness, and a low density mass seen on the plain abdominal tomography can indicate a suspicious mass, and the retroperitoneal tumors can be also observed by CT, MRI, and ultrasonography [6
The main treatment is extensive surgical resection and then these tumors are often treated with concurrent chemotherapy and radiation therapy to reduce the possibility of local recurrence and metastasis. It has been reported that the average five-year survival rate of patients with malignant fibrous histiocytoma is 59% to 66.7% and the local recurrence rate is 16% to 31% [7
]. The prognostic factors to predict local recurrence and distant metastasis include the patient's age, a history of recurrence, the tumor size and depth of invasion, the histological grade of the mass and the status of the resection tumor margin. The histological grade of the emass and the status of the resected tumor margin are the most reliable predictors of the prognosis [8
However, it is often impossible to conduct the extensive resection without damaging the capsule of the mass when soft tissue sarcoma such as malignant fibrous histiocytoma occurs in the retroperitoneal cavity. For the mass of this report, we thought that the mass was radically resected (< 2 cm distance from the tumor) with a negative marginal status when the primary surgical resection of the tumor was conducted, but we think the recurrence occurred due to microscopic residual tumor and the local recurrence occurred at a more rapid rate because postoperative concurrent treatment was not conducted. Thus, we can say that it is of great importance to conduct the concurrent treatment with postoperative chemotherapy and radiation therapy when malignant fibrous histiocytoma with a higher recurrence rate occurs in the retroperitoneal cavity rather than in the limbs. The effect of these treatments are still controversial, but Feldman and Norman [9
] reported that irradiation reduced the size of the mass, and Simon and Enneking [10
] reported that one patient among the cases of lung metastasis of malignant soft tissue tumor completely recovered from multiple pulmonary nodules in both lungs after radiation and dactinomycin therapy.
For our current case, considering that the age of the patient was the late 60s and the size of the tumor was larger than 5 cm with iliac involvement and the histological grade was also high, we can predict that there is a great possibility of local recurrence or distant metastasis into the lung in the future. In addition, when malignant fibrous histiocytoma occurs in the retroperitoneal cavity, despite the fact that it was successfully treated with surgical resection, the histological grade is high and this type of tumor has a high likelihood of local recurrence in the case with poor prognostic factors for local recurrence. Therefore, we think that concurrent treatment with chemotherapy and radiation therapy after surgery should be conducted and periodic follow up observation should be performed for the early detection of local recurrence and metastasis after surgery. Because the tumor's growth increased over time, we can verify the need for surgical excision as soon as possible when the recurrence occurs.
We performed surgical treatment for a recurrent malignant fibrous histiocytoma that occurred in the left psoas muscle, and we report the MRI findings and the prognostic factors for local recurrence and distant metastasis, along with a review of the relevant literature.