Radiographs show a lytic, usually well-defined lobulated lesion, with no peripheral sclerosis or periosteal reaction. The bone can be slightly expanded, and with tumor growth, the cortex can be destroyed with soft tissue expansion of the lesion.

CT confirms the absence of bone production by the tumor tissue.

MRI imaging usually presents iso- or hypointense signal relative to the adjacent muscle on T1- and a characteristic low signal on T2-weighted images.

CT and MRI help define the soft tissue extension of the lesion.

The cut surface is white and firm, with a whorled pattern and clear, scalloped margins.

More commonly, desmoplastic fibroma has a general low cellularity and abundant collagen matrix, with occasional permeation of neighboring tissues.

Cells are spindle and arranged in a whorled fashion or in long fascicles, similar to what happens in soft tissue desmoplastic fibroma. Nuclei look active and may show minimal atypia, and mitoses are absent or rare.

Long, dilated vascular channels are commonly seen.

Thick, undulating collagen fibers resembling keloid may be focally seen.

Reactive bone trabeculae may be focally present in a fractured or recurrent tumor, raising a differential diagnosis with fibrous dysplasia.

MDM2 and CDK4 are negative in desmoplastic fibroma and can differentiate it from low-grade osteosarcoma which will show positivity for these markers.

Beta-catenin is usually positive in the cytoplasm of neoplastic cells.

Rearrangement involving chromosomes 11 and 19 was reported.