Dermatofibrosarcoma protuberans

A dermatofibrosarcoma protuberans (DFSP) is a type of soft tissue sarcoma that occurs just beneath the skin. It involves the middle layer of the skin (the dermis) and fat or other tissues just below it. In longstanding cases, it may also extend into muscle and fascia—tissue that surrounds and supports structures such as muscles, organs, and blood vessels.

Most dermatofibrosarcoma protuberans cases are found on the torso, the part of the body made up of the chest, abdomen (belly), pelvis, and back. Other common locations include the arms, legs, head, and neck.

DFSP is a rare sarcoma. Each year, doctors in the U.S. diagnose 13,000 new soft tissue sarcomas, with DFSP accounting for no more than 1 percent of those cases. It most commonly affects people in their 30s, 40s, and 50s.

While DFSP has a tendency to recur (return) after surgical treatment, it rarely metastasizes (spreads).

The Sarcoma Program at Penn Medicine’s Abramson Cancer Center has a team of the nation’s most experienced DFSP experts. We frequently partner with Penn Dermatology and bring together a full range of specialists, including surgeons focused on particular areas of the body.

Doctors divide dermatofibrosarcoma protuberans into several types, based on the cells they contain and other features:

• Conventional DFSP: Most DFSP cases are this type. Fewer than 5 percent of these tumors spread, and they do so only after cancer has returned several times after treatment.
• Fibrosarcomatous dermatofibrosarcoma protuberans (FS-DFSP): Parts of these cancers look and act more like fibrosarcoma. They’re likely to return and spread.
• Giant cell fibroblastoma: These tumors feature much larger cells. They’re also called juvenile dermatofibrosarcoma protuberans because they affect children and teens most often.
• Myxoid dermatofibrosarcoma: These tumors feature an unusual tissue called myxoid stroma.
• Pigmented dermatofibrosarcoma protuberans: These cancers, also called Bednar tumors, feature dark-colored cells. They occur most frequently in the Black population.

While DFSP does not typically change the way you feel, it often develops in a way you can see:

• Early dermatofibrosarcoma protuberans starts as a firm area just beneath the skin. It can cause the surrounding skin and tissues to turn greyish or red-brown.
• DFSP grows slowly but steadily, with several pimple-like bumps forming, colored either red-brown or violet.
• Tumors can eventually reach up to 5 centimeters across.
• Sometimes a painful, open wound forms.

DFSP forms because of a genetic change involving chromosomes, the structures in cells made of DNA. A gene on chromosome 17 changes places with a gene on chromosome 22. Researchers don’t yet understand why this gene change happens with DFSP. This genetic change is not inherited and cannot be passed down to children.

Genetic changes that can be caused by exposure to certain chemicals, previous medical treatments, or unusual genetics inherited from a parent are found in other soft tissue sarcomas. It’s still unclear if any of these risk factors apply to DFSP.

There is some evidence that a previous skin injury could raise the risk of developing DFSP. Some of these tumors develop in places on the skin with scars or tattoos. Researchers are actively studying this possible link.

Diagnosing dermatofibrosarcoma protuberans starts with a physical exam and a discussion about when you first noticed changes to the skin. One of our doctors will perform a needle biopsy to take a small amount of the tumor for evaluation. Specialized team members look at the tissue sample under a microscope and perform lab tests on it, including tests that look for the genetic changes involved.

In some cases, we may also recommend imaging tests. Magnetic resonance imaging (MRI) can provide more details about the tumor’s size and whether it has grown into other surrounding tissue. This information can help guide our treatment planning, to provide you with the best recommendations.

DFSP treatment at Penn Medicine focuses on surgically removing the cancer. There are two ways to do this.

One type of procedure is called Mohs surgery. With Mohs, our surgeons remove one layer of skin at a time. After each layer, they pause to check for cancer. They keep removing layers until they see evidence that all cancer is removed.

The other option is to remove the DFSP in one piece with a buffer of normal tissue, rather than layer by layer. Removing the DFSP with a clean margin gives the patient the best chance to avoid having it return in the same spot. If the margins are not clean, radiation therapy may be recommended.

If a DFSP can’t be removed, or for tumors that return or spread, our team can treat DFSP with a targeted therapy called imatinib. This drug stops a particular cellular growth pathway that DFSP needs.

Given the chance that DFSP can return, we recommend checkups after treatment on a set schedule.