This is a relatively common soft tissue sarcoma and accounts for up to 1% of all soft tissue sarcomas in adults.
Its peak incidence is in young adulthood, but the incidence in childhood is unknown
This tumor occurs generally on the trunk and extremities.
Regarded as an intermediate tumor and not high grade. This tumor grows slowly. If incompletely excised DFSP may recur locally, but is very rarely associated with distant metastatic disease.
Multiple local recurrences may be associated with de-differentiation to a high grade sarcoma and distant metastatic disease.
Cytogenetic abnormality:
- DFSP is characterized by the presence of a recurrent translocation t(17;22)(q22;q13)
- There may also be supernumerary ring chromosomes containing material from the chromosomal regions 17q22 and 22q13 accompanied by simple chromosome trisomies.
- The translocation results in the fusion of the alpha chain type 1 of collagen (COL1A1) gene with the platelet derived growth factor Beta (PDGFbeta) gene
- Fluorescence in situ hybridization (FISH) can be used to show the t(17;22) using gene specific probes to demonstrate the PDGFbeta gene rearrangements as well as genetic gains and losses
The result of this rearrangement is upregulation of a COL1A1-PDGFB fusion protein that is processed to a mature PDGF-BB homodimer, which activates the PDGFB receptor (PDGFRB), a protein tyrosine kinase acting as a potent growth factor. These mechanisms contribute directly to development and growth of DFSP
The gross appearance can be consistent with a plaque or a multinodular subcutaneous tumor with purplish nodules.
Histopathology:
- Monotonous storiform pattern of uniform, cytologically bland spindle cells
- Honeycomb pattern of infiltration into the subcutaneous fat
- Immunohistochemical staining
- Strongly positive for vimentin and CD34
- Negative for factor XIIIa staining
- Apolipoprotein described as a marker for DFSP
Therapy
Complete surgical excision with negative margins is the mainstay of therapy
Systemic therapy
- Imatnib (small-molecule tyrosine kinase inhibitor) can be used as adjuvant therapy and has been shown in studies to induce regression of DFSP.
References and Resources:
DFSP at the Atlas of Genetics and Cytogenetics in Oncology and Haematology
