Myxofibrosarcoma is one of the most common sarcomas in the elderly. It was first described in 1977, and it represents a spectrum of myxoid fibroblastic sarcomas, the high-grade end of the spectrum of what was formerly labeled as “myxoid malignant fibrohistiocytoma” [2
]. Currently, the World Health Organization recognizes myxofibrosarcoma as a distinctive entity, marked by distinctive clinicopathologic characteristics [1
]. Compared to other sarcoma subtypes, the prognosis of myxofibrosarcoma is relatively good, with an overall risk of metastases ranging between 20% and 25% [4
In the present case, spindle-shaped tumor cells were sparsely distributed in the abundant myxoid matrix. The cellularity was remarkably low, and tumor necrosis was not obvious. From these findings, the present case was diagnosed as grade 1 myxofibrosarcoma. Tumor grades, as in the most soft tissue sarcoma subtype, predict the risk of developing distant metastases. Generally, grade 1 cases have been considered to be incapable of metastatic disease [6
]. Most of the patients who eventually developed metastatic disease reported in the several literatures had grade 2 or 3 myxofibrosarcoma [6
]. Within our knowledge, only a few cases with grade 1 myxofibrosarcoma including the current case developed metastatic lesions [10
The diameter of the tumor was also a risk factor for the establishment of distant metastases [9
]. In the current case with grade 1 myxofibrosarcoma, we decided to perform the planned inadequate resection to reduce the functional disability and to spare the lower limb. For the prevention of local recurrence, we delivered postoperative radiation therapy. The current case had a deep-seated large tumor sized more than 20
cm in diameter, and therefore, the current case still had a high risk of the development of metastatic lesions. As a result of the limb sparing surgery, rapid development of local recurrence and multiorgan dissemination had developed. More radical surgical management including amputation was mandatory even for the current case with a grade 1 myxofibrosarcoma.
The present case was remarkably hypocellular and only slightly pleomorphic in histology that made us diagnose grade 1 myxofibrosarcoma. However, the patient developed fatal metastases in multiple vital organs. These facts remind us that myxofibrosarcoma can grow and spread rapidly even if its malignant histopathological grade is extremely low. Our observation suggests that the strict managements of the primary tumors are necessary even for patients with low-grade myxofibrosarcoma, especially in the cases located in the deep layer with extremely large size.