Dermatofibrosarcoma protuberans (DFSP) is a rare soft tissue tumor arising in the dermis of the skin. It occurs in about 1 in 100,000 to 1 in 1 million individuals, with the incidence being doubled in black people. However, the incidence is rising among Caucasians, especially those living in Hawaii.
Women have a slightly higher risk of developing these tumors, and they tend to show accelerated tumor growth during pregnancy.
There are certain risk factors that worsen the prognosis for this condition, such as:
- Residual disease following excision
- Fibrosarcomatous change within the tumor
- Higher grade of tumor
- Older age at diagnosis
The mainstay of treatment for this tumor remains surgery with negative margins. Two techniques are in use currently, namely, wide excision and Mohs micrographic surgery.
Wide excision is aimed at removing the tumor with a wide margin of skin until tumor-free skin is thought to have been reached. The presence of almost invisible tentacle-like extensions around the tumor makes this difficult to achieve in some cases, however. For this reason, a frozen section is studied and repeat resection needed if the margins are found to be still positive for tumor cells.
Mohs surgery is more tedious and time-consuming, but many surgeons consider this to be the gold standard for treatment of primary and recurrent DFSP. This is because it focuses on careful histologic evaluation of the removed tissue to ensure a negative margin before the surgery is completed. Better tumor clearance with less extensive surgery is the main reported advantage of this procedure.
Treatment of Recurrences
Prolonged follow up is mandatory for all DFSP patients following either type of surgical excision. Most recurrences occur within 3 years, and about 7 out of every 100 patients will have a local recurrence within 5 years. This is treated by another surgery, following which the cure rate is pushed up to more than 98%.
Radiation therapy is often recommended following surgery on DFSP. This was found to reduce the odds of local recurrence and inactivate more of the tumor cells at the site. This is especially so if patients have positive or close tumor margins or are otherwise at risk for residual disease after excision.
In some patients who are not fit for surgical treatment or who have inoperable disease, chemotherapy has been attempted. The agent used is a tyrosine kinase inhibitor called imatinib mesylate. It inhibits the tyrosine kinase, which is the receptor for platelet-derived growth factor, one of the abnormally high cytokines that are thought to be responsible for tumor growth in DFSP. This therapy is also being used in metastatic or recurrent disease. It has a 50% response rate in inducing remission in these patients. Thus, this drug is being used in certain setups as an adjuvant or neoadjuvant chemotherapeutic agent. This is for patients who have positive surgical margins, or for very large infiltrating primary tumors in order to reduce the volume of the tumor before surgery, respectively. This treatment is not indicated in the minority of patients without the t(17;22) translocation.