Malignant haemangiopericytoma of the knee joint: MR findings

Soft tissue solitary fibrous tumor. Imaging findings in a series of nine cases

OBJECTIVE

Few articles have been published regarding the imaging characteristics of soft tissue solitary fibrous tumors (SFT). The aim of this study is to describe the radiological features in a series of nine patients and to compare these results with pathological and clinical outcome.

SUBJECTS AND METHODS

Nine cases of soft tissue SFT, confirmed by an experienced tumor pathologist, were studied with imaging techniques (US and MRI). Tumor location, size, morphology, local invasion, vascularity, MRI signal intensities, and dynamic contrast-enhancement patterns were recorded. Tumors were subclassified into cellular, fibrous, and giant cell forms histologically.

RESULTS

The most common findings were a well-defined, polylobulated mass that tended to displace adjacent structures. The extremities were the most frequent site of presentation. The tumors showed high vascularity in all imaging studies. The radiological features that correlated better with malignant criteria were tumor size, heterogeneous signal intensity, and heterogeneous uptake of contrast on MRI. On dynamic contrast-enhanced (DCE) sequences, three tumors showed a biphasic curve (type IV) and one a progressive uptake curve (type II). The latter recurred twice after extensive local surgery and was classified as a giant cell variant.

CONCLUSION

In this study a retrospective review of nine new cases of soft tissue SFT was carried out. The presence of a large solid, highly vascularized mass with a prominent vascular pedicle that displaces adjacent structures may suggest the diagnosis of an SFT. DCE sequences might help identify those tumors with worse clinical outcome, but a study with a larger series of patients is needed.