Dermatofibrosarcoma protuberans

Dermatofibrosarcoma protuberans (DFSP) is a very rare tumor. It is a rare neoplasm of the dermis layer of the skin, and is classified as a sarcoma. There is only about 1 case per million per year. DFSP is a fibrosarcoma, more precisely a cutaneous soft tissue sarcoma. In many respects, the disease behaves as a benign tumor, but in 2-5% of cases it can metastasize, so it should be considered to have malignant potential. It occurs most often in adults in their thirties; it has been described congenitally, in children, and the elderly. It accounts for approximately 2-6% of soft tissue sarcoma cancers.

Presentation
About 90% of DFSPs are low grade sarcomas. About 10% are mixed; they contain a high-grade sarcomatous component (DFSP-FS); therefore, they are considered to be intermediate-grade sarcomas. All DFSPs rarely lead to a metastasis (fewer than 5% do metastasise), but DFSPs can recur locally. DFSPs most often arise in patients who are in their thirties, but sometimes have been described in children or the elderly.

Pathophysiology
Over 90% of DFSP tumors have the chromosomal translocation t(17;22). The translocation fuses the collagen gene (COL1A1) with the platelet-derived growth factor gene. The fibroblast, the cell of origin of this tumor, expresses the fusion gene in the belief that it codes for collagen. However the resulting fusion protein is processed into mature platelet-derived growth factor which is a potent growth factor. Fibroblasts contain the receptor for this growth factor. Thus the cell "thinks" it is producing a structural protein, but in fact produces a self-stimulatory growth signal. The cell divides rapidly and a tumor forms.

The tissue is often positive for CD34.

Treatment
Treatment is primarily surgical, with chemotherapy and radiation therapy sometimes being used.

The NCCN guideline recommends CCPDMA or Mohs surgery for the best cure rate of DFSP.

Mohs surgery can be extremely effective. It will remove the tumor and all related pathological cells without a wide-area excision that may overlook sarcoma cells that have penetrated muscle tissue.

The standard of care for patients with DFSP is surgery. Usually, complete surgical resection with wide margins is performed. The addition of adjuvant radiotherapy (irradiation) improves local control in patients with close or positive margins during the surgery. A special surgical technique, the "Mohs micrographic surgery" (MMS), can be employed in patients with DFSP. MMS is technically possible if the DFSP is in an anatomically confined area. A high probability of cure of DFSP can be attained with MMS as long as the final margins are negative. Patients who have a recurrent DFSP can have further surgery, but the probability of adverse effects of surgery and/or metastasis is increased in these patients.

Imatinib is approved for treatment. As all medicinal drugs which have a name that ends on -ib, imatinib is a small molecular pathway inhibitor; imatinib inhibits tyrosine kinase. It may be able to induce tumor regression in patients with recurrent DFSP, unresectable DFSP or metastatic DFSP. There is clinical evidence that imatinib, which inhibits PDGF-receptors, may be effective for tumors positive for the t(17;22) translocation.