Section Editor: Allison Osmond MD FRCPC
June 10, 2026
Pleomorphic dermal sarcoma (PDS) is a rare type of skin cancer that usually affects older adults with extensive sun damage. It most often appears on the scalp or face, areas that receive a lot of ultraviolet (UV) light over a lifetime. PDS is closely related to a lower-risk tumor called atypical fibroxanthoma (AFX); the two look very similar under the microscope, but PDS grows into deeper tissue and carries a higher risk of coming back after treatment and, less commonly, of spreading. For this reason, it is treated and followed more closely.
This article explains what a diagnosis of PDS means, what the findings in your pathology report describe, and how those findings guide the decisions you and your care team make together. Most people whose tumor is completely removed do very well.
What causes pleomorphic dermal sarcoma?
PDS is caused by long-term damage to the skin from ultraviolet (UV) radiation, often described as actinic (sun) damage. This damage builds up over many years, which is why the tumor usually appears on skin that has had heavy lifetime sun exposure. PDS may arise in skin that has already shown other sun-related changes, such as actinic keratosis or squamous cell carcinoma. The tumor cells often carry genetic changes (mutations) in genes that control cell growth, such as TP53, the TERT promoter, NOTCH, CDKN2A, and CDKN2B. These same changes are found in other UV-related skin cancers.
Who gets pleomorphic dermal sarcoma?
PDS usually affects older adults, most often people in their 70s or 80s. It is more common in men and in people 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 are the symptoms of pleomorphic dermal sarcoma?
PDS typically appears as a firm, quickly growing lump on sun-damaged skin, most often on the scalp or face. The lump can range from less than one centimeter to several centimeters across, and in many cases, its surface breaks down, forming an open sore (an ulcer). It is usually painless, though it may become uncomfortable if irritated or infected. Because it grows quickly, it is often noticed suddenly, either by the patient or during a routine skin check.
How is the diagnosis made?
The diagnosis is made after a sample of the tumor is examined under the microscope by a pathologist. A small piece is often removed first by a biopsy, but a confident diagnosis usually requires examining the entire tumor after it is removed, because the diagnosis depends partly on how deeply the tumor has grown.
Under the microscope, PDS is centered in the dermis (the middle layer of the skin) and often extends into deeper tissues, such as fat, muscle, or the tough layer covering muscle (fascia). The borders are usually irregular and poorly defined, and the skin surface is ulcerated in more than half of cases. The tumor cells are pleomorphic, meaning they vary widely in size and shape, and many are spindle-shaped with large, irregular, dark nuclei (the part of the cell that holds the DNA); some are multinucleated giant cells (cells with more than one nucleus). The cells divide rapidly, so mitotic figures (dividing cells) are numerous, and atypical mitotic figures may be seen, and areas of tumor necrosis (dead tumor tissue) are common. The cells may grow in bundles (fascicular), in a swirling pattern (storiform), or against a myxoid, fibrous, or keloid-like background.
Because PDS can resemble several other cancers, the pathologist uses immunohistochemistry (special stains that detect specific proteins in cells) to rule them out. There is no single stain that proves a tumor is PDS, so the diagnosis is made by exclusion: the tumor is typically negative for melanocytic markers (such as S100, SOX10, and Melan-A), which helps rule out melanoma; negative for cytokeratins, which helps rule out carcinoma; and negative for CD34, ERG, and desmin, which helps rule out certain other soft tissue tumors. The cells are usually positive for one or more nonspecific markers such as CD10, CD99, or PDGFRB, which support the diagnosis without proving it. Once the diagnosis is made, imaging may be used to see how far the tumor has grown and to check for spread.
Histologic grade
PDS is not given a numeric grade. The grading systems used for many soft tissue tumors are not applied here; instead, the diagnosis itself reflects higher-risk features, such as growth into deeper tissue, tumor necrosis, or invasion of nerves or vessels. PDS sits at the higher-risk end of a spectrum, with atypical fibroxanthoma at the lower-risk end. Your report will therefore not include a numeric grade, as is expected for this diagnosis.
Perineural invasion
Perineural invasion means that tumor cells are seen attached to or growing along a nerve. Nerves run throughout the body and carry signals such as temperature, pressure, and pain. Perineural invasion is one of the features that distinguish PDS from atypical fibroxanthoma, and it is important because tumor cells can travel along a nerve into surrounding tissue, making the tumor harder to remove completely and increasing the risk that it will come back. Your report will state whether perineural invasion is present.
Lymphovascular invasion
Lymphovascular invasion means that tumor cells are seen inside a blood vessel or a lymphatic channel. Blood vessels carry blood, while lymphatic channels carry a clear fluid called lymph. These vessels give tumor cells a route to spread to lymph nodes or distant organs, so the presence of lymphovascular invasion is associated with a higher risk of spread and, like perineural invasion, is one of the features that separates PDS from atypical fibroxanthoma. Your report will state whether it was seen.
Surgical margins
A margin is the rim of normal-looking tissue removed around the tumor during surgery. Because complete removal is the most important factor in preventing PDS from coming back, the margin status is a key part of the report.
- Negative margin — No tumor cells are seen at the cut edge, which suggests the tumor was completely removed. The pathologist may also record the distance from the nearest tumor cells to the edge, because a wider clear margin is associated with a lower risk of recurrence.
- Close margin — Tumor cells are near the cut edge but do not reach it. Depending on the distance, your doctor may discuss further surgery or radiation.
- Positive margin — Tumor cells are present at the cut edge, which means some tumor may remain. A positive margin is associated with a higher risk that the tumor will return at the same site and usually leads to further surgery or radiation.
Lymph nodes
Lymph nodes are small immune organs found throughout the body. Most PDS tumors do not spread to lymph nodes, but it can happen, so nodes are usually examined only when they feel enlarged or look suspicious on imaging. If a node is removed, the report will state how many nodes were examined and how many contain tumor.
What is the difference between pleomorphic dermal sarcoma and atypical fibroxanthoma?
Atypical fibroxanthoma (AFX) looks very similar to PDS under the microscope, and the two are considered parts of the same family. The difference is how far the tumor has grown. AFX is confined to the upper layer of the skin and does not invade deeper tissue, nerves, or blood vessels. When a tumor shows growth into deeper tissue, tumor necrosis, or perineural or lymphovascular invasion, it is diagnosed as PDS rather than AFX. This distinction matters because PDS has a higher risk of recurrence and spread, which is why it is monitored more closely. It is also why a confident diagnosis usually requires examining the whole tumor rather than a small biopsy.
What is the prognosis?
Most people with PDS do very well when the tumor is completely removed. Compared with many other skin tumors, however, PDS carries a higher risk of returning or spreading. Local recurrence occurs in roughly 20% of cases, most often when the tumor was not completely removed. About 10% may spread to nearby lymph nodes, and around 12% may eventually spread to distant organs, particularly when the tumor has come back. People with weakened immune systems may be at higher risk of spread. There is no single formal staging system for PDS; what matters most for the outlook is whether the tumor has been completely removed and whether it shows higher-risk features.
Features in the pathology report associated with a higher risk that the tumor will return or spread include:
- Positive or close margins — Tumor at or near the cut edge is the main reason PDS comes back at the same site.
- Deep invasion — Growth into fat, muscle, or fascia.
- Perineural invasion — Tumor growing along nerves.
- Lymphovascular invasion — Tumor inside blood or lymphatic vessels.
- Tumor necrosis — Areas of dead tumor tissue.
- Large tumor size — Larger tumors are harder to remove completely.
- Recurrent tumor — A tumor that has already come back once is more likely to spread.
- Weakened immune system — Associated with a higher risk of spread.
What happens after this diagnosis?
The main treatment for PDS is complete surgical removal of the tumor with a clear margin of normal tissue, which is the most effective way to prevent it from coming back. Depending on the size and location of the tumor, this may be done by wide local excision or by Mohs micrographic surgery, a technique in which the tumor is removed in thin layers that are checked under the microscope during the operation. Mohs surgery is often used for tumors on the scalp and face, where it helps achieve complete removal while sparing healthy tissue.
Radiation therapy may be considered after surgery when there are higher-risk features, such as a positive margin that cannot be removed with more surgery or extensive perineural invasion, and it can also be the main treatment for people who are not candidates for surgery. In the uncommon situation where PDS has spread to lymph nodes or distant organs, the care team may consider additional treatment; because these tumors are driven by UV damage and tend to carry a large number of mutations, immunotherapy (treatment that helps the immune system attack the cancer) may be an option in advanced disease. After treatment, regular follow-up examinations are important to watch for recurrence or spread, and because the skin is sun-damaged, ongoing skin checks and sun protection help detect and prevent other skin cancers. Care is usually coordinated by a dermatologist together with a surgeon (often a Mohs surgeon), a radiation oncologist, the pathologist, and, for advanced disease, a medical oncologist.
Questions to ask your doctor
- Was the tumor completely removed, and were the margins clear?
- Was the tumor confined to the skin, or did it grow into deeper tissue, nerves, or blood vessels?
- Was perineural or lymphovascular invasion seen?
- Could this have been atypical fibroxanthoma, or were there features that make it pleomorphic dermal sarcoma?
- If the margins were positive, do I need more surgery or radiation?
- Would Mohs micrographic surgery be a good option, especially on my scalp or face?
- What is the chance that the tumor will come back or spread?
- Do I need any imaging or lymph node evaluation?
- How often should I have follow-up examinations?
- Am I at higher risk because of a weakened immune system?
- What can I do to protect my skin from further sun damage?
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