Pleomorphic dermal sarcoma

by Jason Wasserman MD PhD FRCPC
July 4, 2025

Pleomorphic dermal sarcoma (PDS) is a rare type of skin cancer that usually affects older adults, especially those with extensive sun damage on their skin. It most often appears on the scalp or face, areas that have received a lot of ultraviolet (UV) exposure over time.

PDS is considered related to another tumour called atypical fibroxanthoma (AFX), but unlike AFX, PDS can invade deeper tissues and has a higher risk of recurrence and spread. For this reason, it is treated more aggressively and monitored closely after diagnosis.

Where does pleomorphic dermal sarcoma occur?

PDS most commonly develops in the head and neck area, particularly on the scalp, in individuals with light skin and significant sun exposure. It may also appear in other sun-exposed parts of the body, but this is less common.

What are the symptoms of pleomorphic dermal sarcoma?

Pleomorphic dermal sarcoma typically presents as a firm, rapidly growing lump on the skin. The tumour is most often found on areas of the body that have had long-term sun exposure, especially the scalp and face. The lump may range in size from less than one centimeter to several centimeters across, and in many cases, the surface of the tumour becomes ulcerated, forming an open sore. The tumour is typically painless, although some people may notice discomfort if the lesion becomes irritated or infected. Because it grows quickly, the tumour may be noticed suddenly by the patient or during a routine skin check by a healthcare provider.

Who gets pleomorphic dermal sarcoma?

PDS usually affects older adults, most often people in their 70s or 80s. It occurs more frequently in men and in those with fair skin who have had long-term sun exposure. People with weakened immune systems (such as those who have had an organ transplant or who are being treated for blood cancers like chronic lymphocytic leukemia) may also be at higher risk.

What causes pleomorphic dermal sarcoma?

PDS is caused by long-term damage to the skin from ultraviolet (UV) radiation, also known as actinic damage. In most cases, this damage accumulates over many years due to sun exposure. The cancer may arise in skin that previously had other sun-related skin problems, such as actinic keratosis or squamous cell carcinoma.

Genetic changes have been found in tumour cells from PDS, including mutations in genes that help regulate cell growth (such as TP53, TERT, NOTCH, CDKN2A, and CDKN2B), which are also commonly found in other UV-related skin cancers.

How is pleomorphic dermal sarcoma diagnosed?

The diagnosis is typically made after your doctor performs a biopsy to remove a small piece of the tumour. A pathologist then examines the tissue under a microscope. The diagnosis of PDS is based on a combination of microscopic appearance and immunohistochemistry. A key part of the diagnosis is ruling out other tumours that may look similar, including melanoma and poorly differentiated carcinoma.

What does pleomorphic dermal sarcoma look like under the microscope?

When examined under the microscope, pleomorphic dermal sarcoma typically shows the following features:

• The tumour is centred in the dermis (the middle layer of the skin) and often shows infiltration into deeper tissues, including fat, muscle, or fascia.

• The borders of the tumour are often irregular and poorly defined, and ulceration of the skin surface is seen in more than half of cases.

• The tumour cells are pleomorphic (vary widely in size and shape). Many are spindle-shaped with large, irregular, dark-staining nuclei. Some cells are multinucleated giant cells (cells with more than one nucleus).

• Mitotic figures (dividing tumour cells) are numerous, and abnormal mitotic figures may be observed.

• Tumour necrosis (areas of dead tumour tissue) is common.

• In some cases, the tumour invades lymphatic vessels, blood vessels, or nerves (called lymphovascular or perineural invasion), features that are associated with a higher risk of recurrence or spread.

The tumour may also have one of several patterns:

• Fascicular (cells growing in bundles).

• Storiform (a swirling or whorled pattern).

• Myxoid, fibrous, or keloid-like stromal backgrounds.

Immunohistochemistry

Immunohistochemistry is a special test that helps pathologists confirm the diagnosis by detecting specific proteins made by tumour cells. This test also helps rule out other types of cancer that may look similar under the microscope.

In pleomorphic dermal sarcoma, the tumour cells are typically negative for markers found in other types of skin cancer, including:

• S100, SOX10, and Melan-A (markers seen in melanoma).

• Cytokeratins (seen in carcinomas).

• CD34, ERG, and desmin (seen in other soft tissue tumours).

The tumour cells are usually positive for at least one or more non-specific markers such as CD10, CD99, or PDGFRB. Some tumours may also show limited or focal staining for SMA (smooth muscle actin) or CD31 (a blood vessel marker), although these results are not specific to pleomorphic dermal sarcoma.

This immunohistochemical pattern helps support the diagnosis by excluding other tumours and confirming that the tumour lacks features of melanoma, carcinoma, and other soft tissue sarcomas.

What is the difference between pleomorphic dermal sarcoma and atypical fibroxanthoma?

Atypical fibroxanthoma (AFX) is a skin tumour that looks very similar to PDS under the microscope. However, AFX is confined to the upper layers of the skin and does not invade deeper tissue, nerves, or blood vessels.

If a tumour shows deep tissue invasion, tumour necrosis, or lymphovascular or perineural invasion, it is diagnosed as PDS, not AFX. This distinction is important because PDS has a higher risk of coming back (recurrence) or spreading to other parts of the body.

What is the treatment for pleomorphic dermal sarcoma?

The most effective treatment is complete surgical removal of the tumour with a clear margin of normal tissue around it. This helps prevent recurrence. Depending on the location and size of the tumour, one of the following surgical approaches may be used:

• Wide local excision.

• Mohs micrographic surgery (commonly used for tumours on the face or scalp).

If the tumour has spread to nearby lymph nodes or other parts of the body (which is rare), additional treatments such as radiation therapy or systemic therapy may be considered.

What is the prognosis for pleomorphic dermal sarcoma?

Most people with PDS do very well if the tumour is completely removed. However, PDS has a higher risk of coming back than some other skin tumours:

• Approximately 20% of tumours may recur (local recurrence) if not completely excised.

• Up to 10% may spread to nearby lymph nodes.

• Around 12% may eventually spread to distant organs, especially if the tumour recurs.

People with weakened immune systems may be at a higher risk for metastasis. Regular follow-up after treatment is important to watch for recurrence or spread.

Questions to ask your doctor

• Was the tumour completely removed?

• Do I need additional treatment after surgery?

• What is the chance that the tumour will come back or spread?

• How often should I have follow-up exams?

• Is this tumour related to sun exposure?

• Should I take extra precautions to protect my skin in the future?