What is dermatofibrosarcoma protuberans (DFSP)?
DFSP is an uncommon skin tumour arising in the deeper layer of the skin (the dermis). It grows slowly but has a tendency to recur after excision. Luckily, it rarely spreads to other sites beyond the skin.
What causes DFSP?
The cause is unknown, but an injury to the affected skin may be a predisposing factor. Recent advances show tumour cells carry abnormal chromosomes within the tumour cells—t(17;22)(q22;q13)—resulting in the fusion gene COL1A1-PDGFB. This encodes a protein that causes the tumour to grow.
Who is at risk of DFSP?
It usually presents in early or middle adult life between 20 and 50 years of age, but all ages can be affected. The tumour is rare in children. Males are affected slightly more frequently than females. There does not appear to be any racial predilection
What are the signs and symptoms of DFSP?
DFSP usually presents as a painless thickened area of skin (plaque) and/or nodule that feels rubbery or firm to touch and is fixed to the underlying skin. It may be red-brown or skin coloured. It usually grows very slowly over months to years.
Rarely it presents as a soft depressed area of skin making the diagnosis even more difficult. DFSP may range in size from 0.5 to 25 cm in diameter. Fifty to sixty percent of tumours arise on the trunk often in the shoulder and chest area. The remaining 35% of tumours are found on the limbs and 10 to 15% on the head and neck region.
DFSP is often diagnosed when it enters a more rapid growth phase giving rise to larger lesions. Neglected tumours may reach large proportions.
How is DFSP diagnosed?
The absence of symptoms often leads to a delay in diagnosis. Redness and pain only occur in 15% of cases. It is often mistaken for other skin conditions particularly in the early stages. Skin biopsy is needed to confirm the diagnosis.
It has a characteristic appearance under the microscope with densely arranged spindle shaped cells. It may be difficult to assess complete removal.
DFSP's chromosomal abnormalities can be detected using reverse transcription polymerase chain reaction (RT-PCR) or fluorescence in situ hybrydization (FISH).
What is the treatment for DFSP?
Treatment consists of wide excision of the lesion with several millimetres of normal skin around the margins.
Mohs micrographic surgery, which is a special surgical technique to control tumour margins, is sometimes used to check that all the abnormal cells have been excised.
Radiotherapy is sometimes used in addition to surgery. Chemotherapy is ineffective.
The tyrosine kinase inhibitor imatinib mesylate is used to treat rare cases of local advanced or metastatic dermatofibroscarcoma characterised by COL1A1-PDGFB fusion gene, with 50% response rates.
What is the prognosis?
The tumour only metastasises (spread beyond the skin) in 5% of cases. It spreads in 1% via lymphatic vessels to the regional lymph glands and in 4% via the blood stream, most commonly to the lung followed by the brain, bone and heart.
Local recurrences arise in 11-20% of cases, usually within 3 years of initial surgery, so follow-up is important.
- Rutkowski P, Przybył J, Switaj T. Genetics of rare mesenchymal tumors: Implications for targeted treatment in DFSP, ASPS, CCS, GCTB and PEComa. Int J Biochem Cell Biol. 2014 Apr 2. pii: S1357-2725(14)00099–5.
- Malhotra B, Schuetze SM. Dermatofibrosarcoma protruberans treatment with platelet-derived growth factor receptor inhibitor: a review of clinical trial results. Curr Opin Oncol. 2012 Jul;24(4):419–24.
On DermNet NZ:
- Dermatofibrosarcoma Protuberans – Medscape Reference
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