Aggressive Fibromatosis of Desmoid Type – a Pictorial Review

Summary

Deep fibromatosis of desmoid type comprises rare mesenchymal tumors characterized histologically by proliferation of fibroblasts and myofibroblasts. These lesions are characterized by infiltrative growth and local recurrence but an inability to metastasize. They can be located in the abdominal wall (generally in sutures), intra or extraabdominal. The best imaging modality for evaluation and staging of the deep fibromatoses is MR imaging. These well or ill-defined lesions generally present internal hypointense bands, with lack of enhancement in post contrast images (collagen bundles) and are usually centered in an intermuscular location with a rim of fat (“split fat sign”), although invasion of surrounding muscle is frequent. Linear extension along fascial planes (“fascial tail sign”) is also a frequent manifestation in deep fibromatoses and is uncommon with other soft tissue neoplasms. MR image signal intensity has an implication on tumor recurrence, with a higher recurrence rate in lesions with high T2 signal. In surgically untreated lesions, with undergoing radiation or drug therapy, MR surveillance has been used to assess response to treatment with positive results demonstrating decrease in T2 signal, lesion enhancement and lesion size.