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Desmoplastic fibromas are extremely rare bone tumors that do not metastasize but may be locally aggressive. They are considered to be a bony counterpart of soft tissue desmoid tumors and are histologically identical.
Desmoplastic fibroma of bone is rare and mostly found in young adults and adolescents. It accounts for less than 0.1% of all bone tumors 1. There is no sex predilection.
The diagnosis of desmoplastic fibroma is secured by histology and molecular pathology.
Diagnostic criteria according to the WHO classification of soft tissue and bone tumors (5th edition) 1:
bland spindle cell morphology in bone
The following molecular criteria are desirable 1:
absence of GNAS mutations for exclusion of fibrous dysplasia
absence of MDM2 amplification for exclusion of low-grade central osteosarcoma
Usual complaints are pain or deformity. Some patients might also present with a fracture or the tumor might be found incidentally 1.
Desmoplastic fibroma of bone is a tumor made up of spindle cells resembling desmoid-type fibromatosis and features an infiltrative growth pattern 1.
The etiology of desmoplastic fibroma of bone is unknown 1.
The most frequent locations of desmoplastic fibroma of bone include 1-5:
long bones (femur, radius, tibia)
usually located in the metaphysis or diametaphysis
Macroscopically desmoplastic fibroma of bone usually appears as a whorled, creamy-colored tumor due to high collagen content featuring a firm consistency 1.
Microscopic features of desmoplastic fibroma of bone include the following 1:
low cellularity consistent with bland spindle cells in a collagenous matrix
main cell types include fibroblasts, myofibroblasts, and undifferentiated mesenchymal cells 5
Immunohistochemistry stains can be positive for β-catenin 1.
General imaging features of desmoplastic fibroma of bone comprise the following 1-3:
usually well-defined or partly well-defined
narrow transition zone
sometimes with cortical bone destruction and extension into the surrounding tissues
On plain radiographs desmoplastic fibroma of bone will usually show the following characteristics 3-5:
osteolytic or mixed osteolytic / mildly sclerotic matrix
well-defined or partly well-defined margins
possible endosteal scalloping or cortical breakthrough
geographic pattern of bone destruction
often non-sclerotic margins
internal pseudotrabeculation: >90%
no matrix mineralization
widening of the host bone from gradual apposition of periosteal new bone formation: ~90%
CT will show a soft tissue density mass and will show cortical erosion in a high percentage possibly associated with infiltration of the surrounding tissues 3.
In addition to the general imaging features, MRI shines in depicting soft tissue expansion 1,3,4. In addition to the solid tumor component, there might be cystic changes present.
T1: low signal intensity (isointense or hypointense to muscle)
T2: background intermediate to high signal with intrinsic low to intermediate intensity foci within 6,7
T1 C+ (Gd): heterogeneous enhancement
Bone scintigraphy/FDG PET
Desmoplastic fibroma of bone might show increased uptake 1.
The radiological report should include a description of the following:
form and location
tumor margins and transition zone
infiltration of the surrounding tissues
Treatment and prognosis
Despite being benign it is a still locally aggressive tumor. En bloc resection is the current treatment of choice 8.
Due to its rarity, the prognosis is difficult but it is considered a slow-growing progressive tumor, which shows a local aggressive behavior 1.
If left untreated it can lead to the following 1,2:
History and etymology
Desmoplastic fibroma was initially described by the American bone pathologist Henry Lewis Jaffe (1896-1979) in 1958 10.
Conditions which can mimic the presentation and/or the appearance of desmoplastic fibroma of bone include: