Angiofibroma of soft tissue

Last revised by Dr Joachim Feger on 14 Feb 2022

Angiofibromas of soft tissue are benign fibroblastic soft tissue neoplasms permeated by a vascular network that might be found in the periarticular and articular areas of the lower extremities that have been included as a separate entity into the WHO classification of soft tissue tumors in 2020.

Angiofibromas of soft tissue tumors are mostly found in the middle-aged population with a peak incidence in the sixth decade and a slight female predominance. They can generally affect patients of all ages 1.

The diagnosis of angiofibroma of soft tissue is based on typical histological features and molecular pathology.

Diagnostic criteria according to the WHO classification of soft tissue tumors (blue book) 1:

  • uniform bland spindle cells in a variably myxoid or collagenous stroma
  • prominent vascular network with abundant thin-walled branching vessels

The following criterion is desirable:

  • NCOA2 gene rearrangements

The typical clinical presentation is a slow-growing soft tissue mass 1.

Angiofibromas of soft tissue are characterized by uniform and spindle cells in a fibromyxoid matrix permeated innumerable small thin-walled blood vessels 1.

The etiology of angiofibroma of soft tissue is unknown 1.

Soft tissue angiofibromas are usually found in the extremities in particular the lower extremity with a periarticular articular involvement, a subcutaneous or less often intramuscular or deep location. Unusual sites of origin are the back, abdominal wall the pelvis and breast 1-4.

Macroscopically angiofibromas of soft tissue are usually solid nodular or multinodular well-delineated tumors with a shimmering cut surface and a white to yellowish color 1,4.

Histologically angiofibromas of soft tissue include the following microscopic features 1-4:

  • uniform bland spindle cells with regional variations in cellularity
  • variable myxoid to collagenous extracellular matrix
  • prominent vascular network
  • variable inflammatory infiltrates
  • no cytological atypia or nuclear hyperchromasia

Immunohistochemistry stains are variably positive for CD34, epithelial membrane antigen (EMA) and desmin 1,3,4.

Angiofibromas of soft tissue are associated with NCOA2 gene rearrangements 1-4.

Dedicated descriptions of imaging appearances of angiofibroma of soft tissue are still scarce in the literature. A few reports have described it as a well-circumscribed mass. Signal characteristics and enhancement are presumed to be variable subject to the cellular, myxoid, collageneous and vascular content of the lesion 3,4.

  • T1: roughly isointense to skeletal muscle
  • T2: heterogeneous high signal intensity
  • T1C+(Gd): variable from homogeneous to a peripheral enhancement

The radiological report should include a description of the following:

  • form, location and size
  • tumor margins and transition zone
  • relation to adjacent joints
  • relation to adjacent neurovascular structures

Angiofibromas of soft tissue are benign lesions with a benign clinical course. They have rare local recurrences after excision and there is no known risk for metastases 1,3.

Angiofibroma of soft tissue is a fairly newly described tumor entity by Adrián Mariño-Enríquez and Christopher DM  Fletcher in 2012 3-5.

Tumors or conditions which can mimic the presentation and/or appearance of angiofibroma of soft tissue include 3,4:

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