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Dermatofibrosarcoma protuberans (DFSP) is a rare infiltrating soft tissue sarcoma, generally of low grade malignancy, arising from the dermis of the skin and characteristically associated with a specific chromosomal translocation t(17;22).
Prevalence is estimated at 1 in 10,000 and annual incidence is estimated at around 1 in 200,000.
DFSP can present at any age, including infancy and childhood, but usually presents in the 2nd to 5th decade of life. Between 85 and 90% of tumors are low grade lesions, with the remainder classified as the high grade fibrosarcomatous (FS) type. The lesions typically present as an indurated pink or violet-red plaque or nodular mass on the trunk, proximal extremities, or head and neck region. Growth tends to be slow with local infiltration into deeper tissues and a propensity for local recurrence after excision. However, metastases are rare. Occurrence is sporadic.
DFSP is most likely fibroblastic in origin: over 90% of cases are associated with dysregulated platelet-derived growth factor (PDGF) production resulting from chromosomal translocation or a supernumerary ring chromosome derived from t(17;22). The translocation breakpoint most often involves the second exon of the PDGFB gene on chromosome 22 (22q13.1), with fusion to the collagen, type I, alpha 1 gene (COL1A1) on chromosome 17 (17q21.33). This chromosomal translocation results in the upregulation of the PDGFB gene in the form of a fused proto-oncogene COL1A1/PDGFB.
Diagnosis may be suspected on the basis of histological findings on biopsy samples showing features of a well-differentiated fibroblastic tumor with the characteristic microscopic appearance of interwoven fascicles of cells forming a swirling pattern and positive staining for CD34. Cytogenetic analysis identifying the characteristic t(17;22) chromosomal translocation or interphase FISH using split-apart probes for chromosome 22 can be used to confirm the diagnosis. Imaging modalities suchas MRI or CT scans are most useful for assessing the depth of tumor invasion or identifying metastatic sites.
The differential diagnosis should include fibrosarcoma (see this term), dermatofibroma, neurofibroma, and other soft tissue tumors.
Management and treatment
Complete surgical resection with clear margins is the standard treatment for primary and recurrent DFSP. Mohs microscopic surgery (MMS) using sequential horizontal sectioning with immediate microscopic examination may reduce the amount of tissue resected and is associated with a low risk of recurrence. Post-operative radiotherapy can be used when resection is incomplete. Imatinib, an oral PDGF receptor tyrosine kinase inhibitor may be beneficial for patients with an unresectable, locally advanced lesion or with metastatic disease. Cytotoxic therapy is of little proven value.
The prognosis is excellent for low grade lesions but a poorer prognosis is associated with the FS variant due to a higher risk of recurrence and metastases. Overall, the rate of mortality is low (< 3% at 10 years).
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