Dermatofibrosarcoma Protuberans (DFSP)

What DFSP is

DFSP arises from cells in the dermis, the deeper layer of the skin. It belongs to the soft tissue sarcoma family but is usually low-grade, and it behaves very differently from common skin cancers such as basal cell carcinoma. Nearly all cases are driven by a gene change in which parts of chromosomes 17 and 22 swap places, fusing the COL1A1 and PDGFB genes. This fusion makes the cells produce excess growth factor, which drives the tumor. It is not inherited and not caused by anything the person did.

DFSP is rare: roughly 1 to 5 cases per million people per year. It is somewhat more common in Black individuals, in whom a pigmented variant (Bednar tumor) occurs.

What DFSP looks like

DFSP grows slowly, often over years, which is why it is frequently mistaken for a benign lesion.

• Early stage: a firm, flat or slightly depressed patch that may be flesh-colored, pink, red-brown or bluish, resembling a scar, bruise or birthmark.
• Later stage: one or more raised, firm nodules develop on the plaque ("protuberans" means bulging).
• Location: trunk (especially chest and shoulders) in about half of cases; also arms, legs, head and neck.
• Symptoms: usually painless; may become tender, ulcerated or bleed when large.

It is often first diagnosed as a keloid, dermatofibroma, lipoma or cyst.

Diagnosis

1. Skin examination by a dermatologist.
2. Biopsy: a deep incisional or punch biopsy is needed, because shallow shave biopsies can miss it. Under the microscope, spindle cells grow in a "storiform" (cartwheel) pattern and infiltrate fat in a honeycomb pattern.
3. Immunostaining: DFSP cells are usually positive for CD34.
4. Genetic testing for the COL1A1-PDGFB fusion confirms difficult cases and predicts response to imatinib.
5. MRI for large or recurrent tumors, to see how deep and wide the tumor extends before surgery.
6. Chest imaging only for the rare fibrosarcomatous variant or advanced disease.

Treatment

Surgery

Complete removal is the goal.

• Mohs micrographic surgery: the surgeon removes the tumor in layers and examines 100 percent of the edges under the microscope during the procedure, removing more only where cancer remains. Recurrence rates are very low (about 1 to 3 percent in many series), and healthy tissue is spared. It is the preferred approach where available.
• Wide local excision: removal with 2 to 3 cm margins and careful edge examination. Recurrence rates are higher if margins are not fully checked.
• Reconstruction with flaps or skin grafts may be needed for large defects.

Imatinib

Imatinib, a targeted pill that blocks the PDGF receptor, shrinks DFSP in most patients with the gene fusion. It is used for tumors that cannot be removed, for metastatic disease, or to shrink a large tumor before surgery.

Radiation therapy

Used after surgery when margins are positive and further surgery is not possible, or for recurrences.

Outlook

The outlook is excellent when DFSP is completely removed: survival is close to normal life expectancy. Recurrence, usually within the first 3 to 5 years, is the main risk, especially after incomplete removal. Distant spread is uncommon and mostly occurs with the fibrosarcomatous variant or repeated recurrences.

Follow-up

• skin checks of the scar and surrounding area every 6 to 12 months for at least 5 years, then yearly
• report any new lump or thickening in or near the scar

Frequently asked questions

What does dermatofibrosarcoma protuberans look like?

It usually starts as a firm, flat patch that looks like a scar, bruise or birthmark, often pink, red-brown or skin-colored. Over months to years, it thickens and may develop raised, firm bumps. It is commonly found on the chest, back or shoulders.

Is DFSP a cancer?

Yes. DFSP is a low-grade soft tissue sarcoma of the skin. It grows slowly and rarely spreads to other organs, but it invades nearby tissue and often comes back if not completely removed, so it needs specialist treatment.

What is the treatment for DFSP?

Surgery to remove the tumor completely is the main treatment, ideally Mohs surgery, which checks all margins. Imatinib, a targeted drug, is used for large, inoperable or advanced tumors, and radiation is sometimes added after surgery.

Can DFSP come back after surgery?

Yes, recurrence is the main risk, usually within a few years. It is much less likely after Mohs surgery or wide excision with fully clear margins. Regular skin checks at the surgery site help catch any recurrence early.

What is the survival rate for DFSP?

Survival is excellent. With complete surgical removal, nearly everyone survives long term. The rare cases that spread to distant organs, usually the fibrosarcomatous variant, have a less favorable outlook.