Angiofibroma of soft tissue

Angiofibromas of soft tissueare 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 tumours in 2020.

Epidemiology

Angiofibromas of soft tissuetumours 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.

Diagnosis

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

Diagnostic criteria

Diagnostic criteria according to the WHO classification of soft tissue tumours (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

Clinical presentation

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

Pathology

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

Aetiology

The aetiology of angiofibroma of soft tissue is unknown ¹.

Location

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.

Macroscopic appearance

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

Microscopic appearance

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

Immunophenotype

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

Genetics

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

Radiographic features

MRI

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.

Signal characteristics

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

Radiology report

The radiological report should include a description of the following:

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

Treatment and prognosis

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.

History and etymology

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

Differential diagnosis

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

• fibroma of tendon sheath
• solitary fibrous tumour
• synovial sarcoma
• low-grade fibromyxoid sarcoma
• myxoid liposarcoma