Myxoinflammatory fibroblastic sarcoma: spectrum of disease and imaging presentation

To describe the imaging findings of a series of myxoinflammatory fibroblastic sarcomas (MFSs) from our institution, including a case of dedifferentiated MFS and two cases with areas of high-grade tumor, in addition to typical cases of low-grade tumor. To correlate the imaging findings with the pathologic features of these tumors.

IRB approval was obtained. Retrospective search of the pathology database at our institution from 2000 to 2015 identified seven cases of MFS with available imaging. Imaging, pathology, and clinical data were reviewed.

Unlike the majority of well-differentiated tumors in our series (four cases), one tumor showed dedifferentiation and two cases had areas of high-grade tumor. The dedifferentiated tumor showed peripheral post-contrast enhancement. One case with a substantial high-grade component showed osseous destruction and peripheral enhancement in the high-grade area, while the low-grade component enhanced diffusely. The second case had a small high-grade area and showed diffuse enhancement. All three of these cases had non-acral locations and lacked association with a tendon. The four cases of low-grade MFS demonstrated diffuse enhancement, were located in the distal extremities, and were associated with a tendon.

The imaging findings of dedifferentiated and high-grade MFS differ from the more typical low-grade tumors in that they have nonenhancing areas, a non-acral location, lack association with a tendon, and may involve bone. The radiologist should be aware that MFS represents a spectrum that includes low-grade tumors, tumors with high-grade areas, and tumors with dedifferentiation and that this spectrum presents with differing imaging features.