Dermatofibrosarcoma protuberans (DFSP) is a rare tumor affecting the deep layers of the skin. It can occur at any age, including the newborn period, but it is most frequent between the second and fifth decades of life. Women have a slightly higher incidence, and it grows faster than usual during pregnancy. In newborns, it may be mistaken for a birthmark.
The incidence among blacks is approximately twice the incidence that has been observed in whites. However, the incidence in the latter group is rising, especially among white residents of Hawaii. The risk factors for this tumor are yet to be identified, but some cases have been noted to arise in skin that was previously burned or suffered severe trauma. The underlying etiology seems to be genetic, with the translocation t17;22 being found in 90% of all patients affected. This mutation is commonly found as a supernumerary ring chromosome carrying parts of the genes COL1A1 and PDGFB, from chromosome 17 and 22 respectively, in fused form.
While COL1A1 is responsible for the production of collagen type 1, providing support and structural strength to many tissues, the other is a powerful growth factor that enables many cells to grow, proliferate and differentiate. The fused gene results in the production of large amounts of PDGFB, which promotes the proliferation of the mutated clone of cells to form a DFSP tumor.
The lack of symptoms means that presentation is late in most patients. Only less than a fifth of all patients report with pain or redness.
The first sign of DFSP is a soft to firm skin patch that changes little over the months or years in most cases. It is flesh-colored, reddish or purple, and either flat, or raised, or even depressed, in some patients. It may resemble a pimple, a scar or a birthmark.
The margins are irregular in many cases. It has a somewhat shiny surface, but it is hardly ever associated with pain or tenderness until the late stages. It tends to be locally aggressive, but not metastatic. After several years, the tumor may start to grow more aggressively, swell or become painful, or bleed. Additional tumors may appear in the neighbourhood of the original one. The color of these tumors may change to blackish or brownish, and these new tumors grow faster than the original one.
In the early stages, the tumor has three forms:
- A morphea-like form that closely resembles a scar or plaque
- An atrophoderma-like form
- An angioma-like form
In the protuberant stage, the raised nodule is evident, one or more according to the duration of the condition.
The size of the tumor ranges from 1-25 cm, though most are less than 5 cm wide. It occurs most often over the torso (50-60%), extremities (35%), or the head and neck region (10-15%). However, no part of the skin is exempt and DFSP has been reported in the vulva, breast or scalp as well.
The lesion is usually first noticed when it starts to grow rapidly, or becomes more prominent. At this point the growing tumor pushes up the superficial skin to form a firm or rubbery patch, over which the skin is stretched, may become tender, ulcerate, bleed, or feel fixed to the tumor.
The tumor may enter a rapid growth phase during pregnancy.