Giant cell fibroblastomas are locally aggressive mesenchymal neoplasms closely related to dermatofibrosarcoma protuberans.
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Epidemiology
Giant cell fibroblastomas are rare. They are usually but not exclusively found in children within the first decade of life, adult cases are rare. Boys are more commonly affected 1-3.
Associations
Giant cell fibroblastomas are closely related to dermatofibrosarcoma protuberans 1-3.
Diagnosis
The diagnosis of giant cell fibroblastomas is established by location, histological and molecular pathologic criteria 2.
Diagnostic criteria
Diagnostic criteria according to the WHO classification of tumors: soft tissue and bone (5th edition) 2:
- infiltrative borders within the skin and subcutis
- hypocellular lesion with a collagenous or myxoid background
- composition of spindle cells stellate tumor cells and scattered multinucleated giant cells
- irregular branching pseudovascular spaces often lined by multinucleated giant cells
The following diagnostic criterion is desirable:
- COL1A1-1-PDGFB fusion
Clinical presentation
Giant cell fibroblastomas usually present as plaque-like, painless, slow-growing cutaneous lesions 1,2.
Pathology
Pathologically giant cell fibroblastomas are characterized by multinucleated giant cells, pseudovascular spaces and on a molecular basis by a COL1A1-1-PDGFB fusion 2. They usually involve the subcutaneous tissue and the dermis and rarely infiltrate the skeletal muscle superficially 1-3.
Etiology
The etiology of giant cell fibroblastomas is currently unknown 1.
Location
Tumors are most commonly found in the trunk, groin or axillae and far less often in the extremities or head and neck region 1,2.
Macroscopic appearance
Macroscopically tumors are ill-defined infiltrative lesions with a grey to yellowish color and mucoid cut surface. Size can be quite variable ranging from <1 cm to 8 cm with a median size of 3-4 cm 1,2.
Microscopic appearance
Histologically giant cell fibroblastomas are characterized by the following 1-4:
- mainly subcutaneous location with infiltration of the skin and very rarely the skeletal muscle
- honeycomb or parallel growth patterns
- sparing of subcutaneous adnexal structures
- variable cellularity but commonly hypocellular areas in a myxoid to collagenous stroma
- tumor composition of spindle cells, stellate cells and multinucleated giant cells
- wreath-like arrangement of nuclei
- rare mitoses, absent tumor necrosis
Immunophenotype
Spindle cells and multinucleated giant cells usually express CD34 on immunohistochemistry stains 1.
Genetics
COL1A1-1-PDGFB fusions are characteristic 1.
Radiographic features
At the time of writing, there are only very few reports of the radiological features of this entity 4,5.
Ultrasound
On ultrasound a tumor described in one case has been characterized as hypoechoic with well-defined margins and internal irregular septum-like echogenic structures 4.
MRI
On MRI one case showed different signal intensity in the centrum and the periphery on fluid-sensitive T2 weighted images with a bright edge and lower signal in the center 4. Another report described multiloculated vessels and septations within the mass 5.
Signal characteristics
(compared to skeletal muscle)
- T1: iso to hypointense to skeletal muscle
- T2: slightly hyperintense to skeletal muscle
- T1 C+ (Gd): intense peripheral enhancement
Radiology report
The radiological report should include a description of the following:
- form, location and size
- infiltrative tumor margins
- relation to muscular fasciae and skeletal muscles
- relationship to local nerves and vessels
- local lymph nodes
Treatment and prognosis
Management consists of surgical excision, and local recurrences of up to 50% have been described. However, upon wide local excision recurrences are rare 2,3.
History and etymology
Gian cell fibroblastomas were first described by the American pathologist Barry M Shmookler and the Austrian-American pathologist Franz Michael Enzinger in 1982 1,3,6.
Differential diagnosis
Conditions that can mimic the presentation and/or the appearance of giant cell fibroblastoma include the following: