Aggressive fibromatosis of the prevertebral and retropharyngeal spaces: MR and CT characteristics.

A 47-year-old man had aggressive fibromatosis, and CT and MR showed a large, multilobulated soft-tissue mass within the prevertebral and retropharyngeal spaces. On CT, the lesion was slightly higher in attenuation than adjacent muscle; on MR, it was intermediate between muscle and fat on unenhanced T1-weighted images, isointense with fat on intermediate-weighted images, hyperintense relative to fat on T2-weighted images, and markedly enhanced after administration of gadopentetate dimeglumine. Multiple small focal and linear areas of decreased signal intensity that did not enhance with gadopentetate dimeglumine were observed on all pulse sequences.