[Imaging manifestations and pathologic features of soft tissue desmoid-type fibromatosis].

Background & Objective: Soft tissue desmoid-type fibromatosis is a type of benign, infiltrative tumors which are rarely seen. This study was to analyze CT and MR manifestations and pathologic features of soft tissue desmoid-type fibromatosis to improve its diagnostic accuracy.

Methods: A total of 34 soft tissue desmoid-type fibromatosis from 29 patients, including 20 primary and 14 recurrent tumors were analyzed. Eight were scanned with CT, and 26 were scanned with MRI. Features of the growth pattern, CT or MRI findings and pathologic appearances of the tumors were studied.

Results: The mean size of the 34 tumors was 6.5 cm. Of the 34 tumors, 31(91.2%) had an ill-defined or partially ill-defined margin, 31(91.2%) had a lobulated or irregular contour, 17(50.0%) had neurovascular involvement, 15(44.1%) had bone involvement, 23(67.6%) had extra-compartmental extension. Among the eight tumors scanned by CT, six showed slight hypodensity on the non-enhanced CT scan, and seven were inhomogeneously enhanced after contrast injection. Twenty-six tumors scanned by MRI appeared either iso-or slightly hyperintense on T1W images, hyperintense on T2W images, and moderate or intense enhancement after gadolinium administration. Heterogeneous signal intensity was detected in 88.5%(23/26) tumors. Linear and curvilinear areas of signal void interspersed throughout the tumors were found in 22 tumors(84.6%) on both T1W and T2W images. Histologic analysis revealed that the tumor was composed of spindle cells and collagen bundles, with a variable amount of intermingled collagen surrounding the spindle cells. Nuclear atypia was not seen,and occasional mitoses were present in the tumor cells.

Conclusion: The characteristic manifestations of CT or MR images of desmoid-type fibromatosis provide important evidence to discriminate benign and malignant soft tissue tumors.