Dermatofibrosarcoma protuberans (DFSP) is a rare type of cancer in which a soft tissue sarcomatous tumor forms deep in the skin. It begins as a small flat lesion, rarely more than 5 cm across, with neither pain nor tenderness. It may be flesh-colored, but more often reddish or purple.
The tumor is characteristically a slow-growing one, and takes months or years to become a raised nodule. Most DFSP tumors occur in individuals between the ages of 20 and 50 years and appear on the torso, extremities, or the head and neck. However, no age group or community is known to be exempt.
The asymptomatic nature of the lesion means that the presentation is late in most patients. Local recurrence is a problem with this tumor, but metastasis is rare, occurring in only about 5 out of 100 patients.
Variants
There are different forms of the tumor, such as Bednar tumors with melanin-containing dendritic cells, myxoid variants, giant cells variants, and the fibrosarcomatous variant (FS-DFSP), which is rare, but is much more aggressive and has a greater potential for metastasis.
The tumor is locally infiltrative, and this local invasion increases if it is incompletely resected. It may also show extension of growth along the deep subcutaneous tissue lines, into the muscle or even the bone underneath.
Prognostic Factors
The treatment of DFSP is primarily surgical and consists of excising the tumor with a clear surgical margin. This may be done using traditional wide excision or Mohs micrographic surgery. Obtaining a negative margin is the benchmark of optimal surgical treatment of this tumor. Mohs surgery is thought to have a better cure percentage, which makes it the treatment of choice in equipped facilities. Some have found a similar degree of local control, however, with either procedure.
DFSP is a deceptively local-appearing tumor, but has thin indiscernible tentacles that strongly resemble normal collagen. This is frequently missed on excision and therefore leads to local recurrence in many cases. Inadequate tumor excision is therefore a prognostic factor of increased risk for recurrence.
The incidence of local recurrence may be brought down using radiotherapy as a post-operative adjuvant therapy. This is so even in patients who had positive or doubtful margins after surgery, that is, those who have residual disease.
Local recurrence mostly occur within 3 years of the first surgery, but have been known to appear even 10 years later. For this reason, a long and regular follow up is highly recommended. Any local recurrence should be treated surgically just as for the initial surgery.
Provided the surgical margin is negative, the prognosis is considered to be very good. Even the isolated presence of a positive margin is not unduly worrying, provided other high-risk factors are absent.
These include:
- Increased patient age
- High mitotic index of cells within the tumor
- Increased cellularity
These are often present in the FS-DFSP variant, and these patients should undergo a complete resection in order to achieve a clear margin at all costs. In some cases where the factors are suggestive of low risk, and the location of the disease is such as to make removal very difficult, it may be left alone under strict surveillance in view of the difficulty of treating it and the generally good prognosis.
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Further Reading