Angiomatoid fibrous histiocytoma

Last revised by Joachim Feger on 22 Oct 2022

Angiomatoid fibrous histiocytomas (AFH) or angiomatoid fibrous malignant histiocytomas are neoplasms of intermediate biologic potential and are classified as soft tissue tumors of uncertain differentiation.

Angiomatoid fibrous histiocytomas a rare and account for about 0.3% of all soft tissue neoplasms. They have a peak incidence in the first two decades but have been described in all ages. There is no gender predominance 1-4.

The diagnosis of angiomatoid fibrous histiocytomas is established based on a combination of typical clinical, histological and molecular pathological features.

Diagnostic criteria according to the WHO classification of soft tissue and bone tumors (5th edition) 1:

  • presents as a small subcutaneous painless nodule 
  • syncytial-like growth pattern with nodules of epithelioid to ovoid cells
  • pseudovascular spaces
  • a peripheral rim of lymphoplasmacytic cells
  • variable immunoreactivity for desmin, CD99 and EMA

The following criterion is desirable:

  • EWSR1 gene rearrangement (in selected cases)

The typical clinical presentation is a slow-growing painless superficial soft-tissue mass and might resemble hematoma or hemangioma. Rare symptoms include anemia, malaise fever or weight loss 1-4

Angiomatoid fibrous histiocytomas are nodular soft tissue tumors mostly found in the subcutaneous tissue characterized by hemorrhagic cystic areas and a thick pseudocapsule 1,2.

The etiology of angiomatoid fibrous histiocytomas is unknown 1.

Angiomatoid fibrous histiocytomas are most often in the subcutaneous tissues of the following regions in areas where lymph nodes can be found 1-3:

  • extremities:  antecubital fossa, popliteal fossa
  • trunk: axilla, inguinal area
  • head and neck

In addition, they are found in other locations or organs as the vulva, ovary brain, lung, mediastinum retroperitoneum or bone 1.

Macroscopically angiomatoid fibrous histiocytomas are usually firm nodular to cystic masses of variable size and tannish-yellow or whitish fleshy color often with multiple hemorrhagic areas 1.

Angiomatoid fibrous histiocytomas are characterized by four morphological key features 1-3:

  • nodular growth of epithelioid, ovoid or spindle cells with a syncytial appearance
  • hemorrhagic pseudoangiomatous spaces surrounded by tumor cells
  • thick fibrous pseudocapsule with hemosiderin deposits
  • peripheral rim or cuff of lymphoplasmacytic cells

Other histologic features are:

  • few mitotic figures but might be atypical
  • variable number of pleomorphic cells

Immunohistochemistry stains are variably positive for desmin, calponin, epithelial membrane antigen (EMA), CD99 and CD68 1-6.

Angiomatoid fibrous histiocytomas are associated with EWSR1-CREB1 gene fusions in more than 90% and less commonly with EWSR1-ATF1 gene fusions or, in a few cases, FUS-ATF1 fusions 1-6.

Angiomatoid fibrous histiocytomas have been described with a well-circumscribed but otherwise non-specific appearance 3,4.

On plain radiograph angiomatoid, fibrous histiocytomas might appear as a well-delineated soft tissue density lesion in the subcutaneous tissues 4.

On ultrasound angiomatoid, they have been reported to display a heterogeneous hypoechoic echotexture with cystic spaces or possibly fluid levels 4,5 and no significant vascularization on color Doppler 5.

Angiomatoid fibrous histiocytomas have been described as heterogeneous soft tissue density mass predominantly isointense to muscle with hyperdense areas suggesting hemorrhage and hypodense areas indicative of cystic or myxoid changes or necrosis 4.

Several possible features of angiomatoid fibrous histiocytomas have been described for MRI. These include the following 3-7:

  • hypointense pseudocapsule with high signal intensity lymphoplasmacytic infiltrate also named as the double rim sign 6
  • intralesional cystic change
  • peritumoral edema
  • fluid-fluid levels
  • T1: mostly isointense compared to muscle but some variability
  • T2: heterogeneously hyperintense
  • STIR/PDFS: hyperintense
  • T1C+ (Gd): variable internal and fine peripheral enhancement

Angiomatoid fibrous histiocytomas have been reported to show increased uptake of FDG 5.

The radiological report should include a description of the following:

  • form, location and size
  • tumor margins and transition zone
  • relations to the muscular fascia
  • relation to adjacent neurovascular structures
  • relations to other structures or bones

Management of angiomatoid fibrous histiocytomas usually includes wide surgical excision. They show local recurrence in up to 15% of cases and can rarely metastasize into the locoregional lymph nodes or to the lungs.  Deeper locations and incomplete surgical removal are associated with higher rates of recurrence 1-5.

Angiomatoid fibrous histiocytoma was first reported by the Austrian-American pathologist Franz Michael Enzinger in 1979 2-4,8.

Tumors or conditions which can mimic the presentation and/or appearance of angiomatoid fibrous histiocytomas include 2-5:

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