Dermatofibrosarcoma protuberans

aka DFSP, Bednar tumour (pigmented dermatofibrosarcoma protuberans), Fibrosarcomatous dermatofibrosarcoma protuberans

Dermatofibrosarcoma protuberans is a rare, slow-growing cancer of the deeper skin that usually appears as a firm plaque or lump on the trunk and is often mistaken for a scar or cyst for years. Surgery with wide margins cures most people; for the few whose tumour cannot be removed or has spread, the pill imatinib works because almost every one is driven by a single gene fusion it blocks.

Part ofSarcomas (soft tissue, bone, GIST)

Dermatofibrosarcoma protuberans is a low-grade sarcoma of the dermis and subcutis driven in more than nine in ten cases by a translocation fusing COL1A1 to PDGFB, which places the platelet-derived growth factor B gene under a collagen promoter and creates an autocrine loop through the PDGFRB receptor. It presents as a slowly enlarging, indurated plaque or nodule, most often on the trunk or proximal limbs, that infiltrates far beyond its visible edge along fibrous septa. About one in ten tumours contains a fibrosarcomatous component, which raises the recurrence and metastatic risk; metastasis, mostly to lung, otherwise occurs in fewer than one in twenty patients. The pigmented Bednar variant and the giant cell fibroblastoma of children are related tumours with the same fusion.

Surgery is the treatment: wide excision with 2 to 3 centimetre margins to fascia, or Mohs micrographic surgery or its slow variant with paraffin sections, which lets the surgeon trace the finger-like extensions and gives the lowest recurrence rates. Recurrence is a function of margin status, so re-excision of involved margins is standard, and radiotherapy is added when clear margins cannot be achieved at sites such as the head and neck. Fibrosarcomatous tumours are followed with imaging for lung metastases.

Imatinib, which inhibits PDGFRB, produced responses in about half of the 24 patients with unresectable or metastatic disease in the pooled EORTC 62027 and SWOG S0345 phase 2 trials, and was approved for unresectable, recurrent or metastatic dermatofibrosarcoma protuberans in October 2006, one of the first uses of a targeted drug chosen by a fusion. It is also given before surgery to shrink large or awkwardly placed tumours and reduce the defect. Fusion-negative tumours do not respond, so confirming the COL1A1-PDGFB fusion by FISH or sequencing is required before treatment; sunitinib and pazopanib have activity after imatinib failure, and fibrosarcomatous or metastatic disease may need sarcoma-type chemotherapy.

State of the art

Wide excision or Mohs surgery cures the great majority, and margin-controlled surgery has cut recurrence rates sharply.
Imatinib, chosen by the COL1A1-PDGFB fusion, gives responses in about half of unresectable or metastatic tumours and can make surgery possible.
Fusion testing separates responders from the rare fusion-negative tumours that need other treatment.

Red cards

From the labels and guidelines behind the standard of care. Your team's thresholds win.

Emergency services now
Fainting or palpitations
Fainting, near-fainting, or an irregular or racing heartbeat; several kinase inhibitors prolong the QT interval and the labels require ECG and electrolyte monitoring.
Imatinib Pazopanib Sunitinib source
Emergency services now
Bowel perforation
Sudden severe abdominal pain, a hard or very tender abdomen, or abdominal pain with vomiting and fever. Boxed warning for gastrointestinal perforation on bevacizumab.
Pazopanib Sunitinib source
Emergency services now
Bleeding or bruising
Bleeding that will not stop, black or bloody stools, or unexplained bruising when platelets are expected to be low.
Doxorubicin source
Check before combining
Sunitinib with Pazopanib: major interaction
QT: both Sunitinib and Pazopanib prolong the QT interval (known and known risk).. Avoid other QT-prolonging drugs where possible; check ECG and correct potassium and magnesium before and during treatment.
Pazopanib Sunitinib source
Check before combining
Food and drink: Doxorubicin
Cumulative dose: risk rises steeply above 400-550 mg/m² (see the anthracycline calculator).
Doxorubicin source
Check before combining
Food and drink: Imatinib
Take with a meal and a large glass of water.
Imatinib source

See all on the product pages:Doxorubicin Imatinib Pazopanib Sunitinib·Printable cards in the navigator

Anatomy and lymph node drainage

Skin (cross-section): subsites and node stations · wireframe schematic, not to scale

Organ atlas →

Each skin cancer comes from a different cell layer: melanocytes and basal cells at the base of the epidermis, keratinocytes above them, Merkel cells and blood vessels in the dermis; depth of invasion decides the risk.

Subsites

Epidermis (in situ)
Basal layer (melanocytes, basal cells)
Keratinocytes (squamous)
Dermis (invasive; Breslow depth)Classic dermatofibrosarcoma protuberans (DFSP; low grade, dermal and subcutaneous) · Fibrosarcomatous DFSP (higher grade, higher recurrence and metastatic risk) · Bednar tumour (pigmented DFSP) · Unresectable, recurrent or metastatic DFSP (imatinib candidates) · Fusion-negative DFSP (does not respond to imatinib)
Merkel cells (dermal-epidermal)
Dermal vessels (Kaposi)Classic dermatofibrosarcoma protuberans (DFSP; low grade, dermal and subcutaneous)
Acral and mucosal sites

Regional lymph nodes

sentinel node in the draining basin
regional basin (axilla, groin, neck)

Same organ: Melanoma, Basal cell carcinoma, Cutaneous squamous cell carcinoma, Merkel cell carcinoma, Kaposi sarcoma, Skin cancer (all types), BRAF V600-mutant melanoma, Stage III melanoma (after surgery), Stage IIB and IIC melanoma, Advanced melanoma (unresectable stage III and stage IV), Mucosal melanoma, Acral melanoma, Advanced cutaneous squamous cell carcinoma, Locally advanced and metastatic basal cell carcinoma

Who gets it and what has changed

Dermatofibrosarcoma protuberans is a rare sarcoma of the skin, about four cases per million people a year, commonest in adults aged 20 to 50 and roughly twice as common in Black people; it is slow-growing and rarely spreads, but it recurs locally if not excised with wide margins.

Group

skin

Cases by country

Cases by country · GLOBOCAN 2022

All countries →

No country-level case numbers. This cancer is not mapped to a GLOBOCAN site.

Standard of care

5top

Lines of therapy by subgroup →Staging and risk scores →

Decisions you may face

1 with more than one option · full decision page →

One section per setting: the options named, what each is for, the trials behind them, the recorded trade-offs and the questions to ask.

Localised disease Positive margins not amenable to further surgery Unresectable, recurrent or metastatic disease Neoadjuvant After imatinib failure or fibrosarcomatous metastatic disease3

Localised disease

Wide local excision with 2 to 3 cm margins to fascia, or Mohs micrographic surgery with complete circumferential margin assessment; re-excision for involved margins.