Dermatofibrosarcoma protuberans (DFSP) is a type of cancer of the soft tissues, occurring in the skin. It is quite rare, usually affecting people between the ages of 20 and 50 years.
About a thousand new cases arise each year in the US, which translates into an incidence of 1-5 per million and is higher in blacks in comparisson to whites.
The most common site of DFSP is the torso, but the tumor may also occur on the extremities or cephalic end of the body. It seems to have a tentacular grip, which helps it to take root in the surrounding muscle or fat, or the underlying bone. It has a high local recurrence rate following excision, but metastasis is less common, occurring in only 5% of cases.
The clinical features of DFSP begin with the appearance of a small firm patch on the skin, either the same color as the surrounding skin, or purple and/or red. It may eventually become papular. Tumor size may range from 1-5 cm. It may resemble a pimple or a roughened area of the skin, but is not associated with pain or tenderness until it stretches the skin unduly. At this time, it may show some bleeding. It grows faster during pregnancy.
Different types of DFSP exist, including pigmented DFSP or Bednar tumors, melanin-containing dendritic cells that contain dark pigment, myxoid tumors with a lot of myxoid stroma, and giant cell fibroblastoma or juvenile DFSP, which is found mostly in children or adolescents.
While the tumor is slow-growing in most patients, some DFSP growths may show areas with more aggressive characteristics. Here the tissue type resembles fibrosarcomatous tissue. This kind of tumor is named fibrosarcomatous DFSP and has a higher rate of metastasis.
The origin of the tumor is associated with a somatic mutation in the chromosomes 17 and 22, which undergo a translocation or rearrangement of genetic material, represented as t(17;22). This mutation is not inherited, but occurs in the tumor cell clone after birth.
Diagnosis and Treatment
Diagnosis of DFSP is based upon the results of ultrasound imaging, magnetic resonance imaging (MRI) and histologic studies of tumor tissue if a biopsy is taken. CT scans or other body imaging may be performed once the diagnosis is confirmed in order to rule out metastatic disease.
Treatment of local disease is by wide excision or Mohs procedure, which is less extensive, but with equally good results. Post-operative radiation may be required to prevent the tumor from returning. It is also used if the patient is not fit for surgery. Chemotherapy is another alternative in such patients, using experimental immunotherapy drugs like imatinib mesylate, depending on the HLA type.
Reconstructive surgery may be performed if the excision was very deep.
Regular follow up is required including chest X-rays to rule out the spread of disease to the chest, which occurs relatively frequently. The prognosis for long-term survival is good in most cases.