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8 slides generated from the cancer page, with a quiz from the open benchmark and speaker notes that cite the sources. Arrow keys move between slides; Print gives one slide per page.
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.
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.
| Setting | Approach | Guideline |
|---|---|---|
| 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. | not mapped |
| Positive margins not amenable to further surgery | Adjuvant radiotherapy to the tumour bed. | not mapped |
| Unresectable, recurrent or metastatic disease | Imatinib after confirming the COL1A1-PDGFB fusion (EORTC 62027 and SWOG S0345); surgery after response where feasible. | not mapped |
| Neoadjuvant | Imatinib for several months to shrink large or facial tumours before excision. | not mapped |
| After imatinib failure or fibrosarcomatous metastatic disease | Sunitinib or pazopanib; sarcoma-type chemotherapy with doxorubicin for metastatic fibrosarcomatous disease. | not mapped |