Gardner fibromas or Gardner associated fibromas are benign fibrous plaque-like soft tissue masses formed by a haphazard arrangement of collagen fibers usually associated with familial adenomatous polyposis.
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Terminology
The term 'desmoid precursor lesion' is now discouraged 1.
Epidemiology
Gardner fibromas occur in children below the age of 10 years in more than three-quarters of the cases and less frequently in adolescents and young adults. They are approximately equally common in both males and females 1-3.
Associations
Gardner fibromas are strongly associated with familial adenomatous polyposis (FAP) and desmoid fibromatosis 1-3.
Diagnosis
The diagnosis of Gardner fibromas is established by histology and immunohistochemistry 1. Tumor location and patient age are important hints 1.
Diagnostic criteria
Diagnostic criteria according to the WHO classification of tumors: soft tissue and bone (5th edition) 1:
- plaque-like tumor in a paraspinal location or the trunk of children
- arbitrarily arranged coarse collagen fibers with cracks or clefts and bland spindle cells
- CD34 and nuclear ß-catenin expression
Clinical presentation
Like other soft tissue tumors, Gardner fibromas typically present as a painless growing mass, they also might be found incidentally especially if the deep soft tissues are affected 1.
Pathology
Gardner fibromas are characterized by an unsystematic arrangement of coarse collagen bundles with intermittent gaps or clefts and intersprinkled harmless spindle cells 1.
Etiology
The most common causes include mutations in the adenomatous polyposis coli APC gene 1,2.
Location
Gardner fibromas grow to form the superficial and deep soft tissues of various non-visceral anatomic sites within the body. Common locations include the trunk including the paraspinal area and the head and neck 1-5.
Macroscopic appearance
Macroscopically Gardner fibromas are usually poorly circumscribed firm masses showing a rubbery appearance with a white-tannish color 1,4.
Microscopic appearance
The microscopic spectrum of Gardner fibromas includes the following 1,2:
- arbitrary composition of collagen coarse fibers
- scattered clefts and cracks
- interspersed inconspicuous spindle cells
- entrapment of adipose tissue or neurovascular structures at the tissue edges
- sometimes collagenous hyalinized background
Immunophenotype
Immunohistochemistry stains usually express CD34 and often β-catenin. Stains are negative for smooth muscle actin (SMA) 1,2.
Radiographic features
Ultrasound
On ultrasound, Gardner fibromas are usually hyperechoic compared to the surrounding tissues 3.
CT
On CT Gardner fibromas appear as a non-specific isoattenuating soft tissue mass 3.
MRI
On MRI Gardner fibromas appear as plaque-like low-signal intensity tumors but are otherwise non-specific 3,4.
Signal characteristics
- T1: low signal intensity
- T2: low signal intensity
- T1 C+ (Gd): variable
Radiology report
The radiological report should include a description of the following:
- form, location and size
- tumor margins
- relation to adjacent bones and muscular fascia
- relationship to local nerves and vessels
- relationship to other organs
Treatment and prognosis
Gardner fibroma is a benign tumor and management is not clearly defined. Many patients might undergo surgical excision. However, screening for familial adenomatous polyposis in the case of the diagnosis of Gardner fibroma is suggested due to the association 1-3.
History and etymology
Gardner syndrome and ‘surface tumors’ associated with familial adenomatous polyposis have been first described by the American human geneticist Eldon John Gardner in 1951 6.
Differential diagnosis
Conditions that can mimic the appearance of Gardner fibroma include 1:
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