Adult fibrosarcomas are rare, malignant and highly aggressive fibroblastic soft tissue tumors. They constitute a diagnosis of exclusion.
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Epidemiology
Adult fibrosarcomas by more recent definition are rare and make up around 1% of soft tissue sarcomas. They are mostly seen in middle-aged people within the 4th and 7th decade of life and with a minor male predilection 1-3.
Associations
Adult fibrosarcomas have been associated with radiation therapy and foreign implants 1,2.
Diagnosis
The diagnosis of adult fibrosarcomas is established histologically. It is a diagnosis of exclusion 1,2,4.
Diagnostic criteria
Diagnostic criteria of adult fibrosarcoma according to the WHO classification of tumors: soft tissue and bone (5th edition) 1:
- monomorphic spindle cell with not more than moderate nuclear polymorphism
- herringbone or fascicular growth pattern with variable amounts of collagen
- immunohistochemical and molecular exclusion of other diagnoses
Clinical presentation
The typical complaint is a soft tissue mass, which can present with or without pain 1,2.
Pathology
Adult fibrosarcomas have become a diagnosis of exclusion. They are characterized by relatively monomorphic spindle cells growing in a fascicular pattern with variable collagen production also referred to as herringbone architecture 1.
Etiology
The etiology is unclear some adult fibrosarcomas have been found in the field of previous radiation therapy.
Location
Locations, where adult fibrosarcomas are mostly found, include the deep soft tissues underneath the deep fascia of the extremities, the trunk and the head and neck region 1-3.
Macroscopic appearance
Macroscopically adult fibrosarcoma usually appears as a circumscribed tumor of tannish white color and firm consistency sometimes featuring areas of necrosis and/or hemorrhage 1,2.
Microscopic appearance
Microscopic features of adult fibrosarcoma include the following 1:
- relatively monomorphic spindle cells (no high degree of pleomorphism)
- fascicular growth in a ‘herringbone’ architecture
- variable collagen production
- variable mitotic activity
- areas of necroses
Immunophenotype
Immunohistochemistry stains can show restricted expression of SMA or calponin 1.
Radiographic features
Imaging features of adult fibrosarcomas have been described as lobulated, well-defined lesions with fibrous bands and slightly irregular margins as well as relations to the deep fasciae with nodular lumps around the fascia edge 2,3. They displace the surrounding tissues 2.
CT
The CT appearance of adult fibrosarcomas has been described as a soft tissue density mass usually isodense to muscle 2.
MRI
On MRI adult fibrosarcomas have been described to look like a heterogeneous soft tissue mass with low signal intensity band-like fibrous streaks in all sequences. Changes in the deep fascia and associated muscle edema have been described in a higher number of cases 3.
Signal characteristics are usually as follows 2,3,5:
- T1: hypo- to isointense to muscle
- T2: mixed heterogeneous hyperintense signal intensity
- DWI: diffusion restriction
- T1 C+ (Gd): variable, heterogeneous peripheral or spoke wheel enhancement
Radiology report
The radiological report should include a description of the following 3:
- form, location and size
- tumor margins
- relation to and alterations of the muscular fascia
- relationship to local nerves and vessels
- subcutaneous tissue or bony involvement
Treatment and prognosis
Treatment options include surgery complemented by adjuvant radiotherapy and neoadjuvant chemotherapy. Local recurrence depends on tumor residues upon surgical removal. Distant metastases occur in the lung liver and bones, in particular, the axial skeleton. Lymph node metastases are rare. The 5-year survival is around 50% 1-3.
History and etymology
Adult fibrosarcoma was once regarded as the most common soft tissue sarcomas in adults 1. Due to advances in testing methods and changes in diagnostic criteria they have become rare entities and a diagnosis of exclusion 1,2. Many descriptions of ‘fibrosarcomas’ have been made in the 1930s and 1940s of which lesions a high percentage would not fulfill diagnostic requirements according to current standards 6-8.
Differential diagnosis
Conditions that can mimic the presentation and/or the appearance of adult fibrosarcoma include the following 1-4:
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