Imaging features and pathological findings of desmoid-type fibromatosis

Objective: To study the imaging features and pathological basis of desmoid-type fibromatosis. Methods: Imaging and pathological characteristics of 14 histologically confirmed desmoid-type fibromatosis were analyzed retrospectively. The imaging studies included CT and MR imaging without (3, 1) or with (3, 7) intravenous contrast enhancement. Results: The mean size of the tumors was 6.2 cm. Of the 16 tumors, 9 had ill-defined margins, 11 had lobulated or irregular contours. On CT, 7/8 tumors were hypo- or iso-dense; 3 tumors showed moderate to intense contrast enhancement. All 9 tumors were iso- or slightly hyperintense on T₁W MR imaging and hyperintense on T₂W imaging. All 8 tumors showed moderate to intense gadolinium enhancement with linear and curvilinear non-enhancing areas of low signal intensities on T₁WI or T₂WI. The tumor was composed of spindle cells surrounded by variable amount of collagen bundles on light microscopy. There was no nuclear atypia or mitosis. The collagen fibers showed hyaline and mucinous degeneration. Conclusion: The imaging features of desmoid-type fibromatosis correlate well with pathological appearance. MRI can demonstrate local tumor spread better than CT for treatment planning. (authors)