Thigh desmoid-type aggresive fibromatosis

Case contributed by Dalia Ibrahim
Diagnosis certain


Right posterior thigh swelling.

Patient Data

Age: 15 years
Gender: Female

Right posterior thigh irregular inter-muscular soft tissue mass lesion. The lesion measures 8 x 9cm in max axial diameters. It elicits heterogeneous signal with linear bands of dark signal on all pulse sequences (band sign). It shows marked contrast enhancement with nonenhancing linear band. It also shows feathery margins giving the (flame sign). the lesion displaces the adjacent muscles with surrounding fat rim giving the (fat rim sign). It encases the patent popliteal vessels.

Biopsy of the lesion showed fibromatosis.

Case Discussion

The case presented typical MRI features of desmoid-type fibromatosis including:

  • It showed reduced T2 signal secondary to high collagen contents with linear bands of persistent dark signal (band sign), however, this band sign is not very specific as it could be seen in giant cell tumor of the tendon sheath and myxofibrosarcoma
  • moderate to marked enhancement especially in the non-fibrotic high cellular components of the mass
  • It was surrounded by a fat rim giving the (fat split sign) and had feathery margins giving the (flam sign)

Desmoid-type fibromatosis or aggressive fibromatosis is an aggressive fibroblastic tumor.

Desmoid tumors are classified according to their location into:

  • abdominal wall desmoid
  • intra-abdominal desmoid
  • extra-abdominal desmoid

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