Desmoplastic melanoma is a rare and unusual form of skin cancer that differs significantly from typical melanomas, affecting mainly older individuals on sun-exposed areas like the head and neck. While challenging to diagnose and treat, new research is revealing that this particular type of melanoma may respond remarkably well to certain immunotherapy treatments.

Therapeutic Approaches for a Challenging Melanoma Subtype

Treating desmoplastic melanoma requires a careful and individualized approach, as this rare form of skin cancer behaves differently from other melanomas. The main goals of treatment include completely removing the cancerous tissue, preventing the cancer from spreading to other parts of the body, reducing the risk of the tumor coming back in the same location, and maintaining quality of life during and after treatment. Because desmoplastic melanoma tends to grow locally in a spreading pattern and often involves nerve tissues, treatment planning must take these characteristics into account.^[1]

The choice of treatment depends on several factors that doctors carefully evaluate for each patient. These include the stage of the disease at diagnosis, how deeply the tumor has grown into the skin layers, whether the cancer has spread to nearby lymph nodes or distant organs, the exact location of the tumor (especially important when it appears on the face or neck), and the patient’s overall health and ability to tolerate different treatments. Additionally, desmoplastic melanoma is divided into two subtypes—pure and mixed—which can influence treatment decisions, as pure desmoplastic melanoma tends to spread to lymph nodes less frequently than the mixed type.^[2]

Treatment approaches generally follow established medical guidelines, but ongoing clinical research continues to explore new and potentially more effective options. The standard treatments have been used successfully for years, while experimental therapies tested in clinical trials offer hope for even better outcomes in the future. Understanding both established and emerging treatment options helps patients and their healthcare teams make informed decisions about the best course of action.

Established Treatment Methods

Surgical excision remains the cornerstone of desmoplastic melanoma treatment for localized disease. This procedure involves removing the visible tumor along with a margin of normal-appearing skin around it to ensure all cancer cells are eliminated. The width of this margin depends on how thick the melanoma measured on biopsy—a measurement called Breslow thickness. For desmoplastic melanoma, surgeons often need to remove wider margins than for other melanoma types because these tumors tend to have microscopic finger-like projections that extend beyond what can be seen with the naked eye.^[3]

Surgery for desmoplastic melanoma can be particularly complex when tumors appear on the head and neck, which occurs in more than half of all cases. The surgery must balance complete cancer removal with preserving important structures like nerves, blood vessels, and facial features. In some cases, reconstructive surgery may be necessary after tumor removal to restore appearance and function. The surgical team carefully plans the procedure to achieve the best possible outcome while minimizing complications and maintaining the patient’s quality of life.^[4]

After the initial wide excision, doctors may recommend a procedure called sentinel lymph node biopsy to determine whether cancer cells have spread to nearby lymph nodes. During this procedure, surgeons identify and remove the first lymph node or nodes that drain lymphatic fluid from the area where the melanoma was located. A pathologist then examines these nodes under a microscope for cancer cells. However, pure desmoplastic melanoma spreads to lymph nodes less frequently than other melanoma types, so the decision to perform sentinel lymph node biopsy is made on a case-by-case basis, considering factors like tumor thickness and whether the tumor is pure or mixed type.^[2]

Radiation therapy represents another important treatment option, particularly in specific situations. This approach uses high-energy beams to destroy cancer cells or prevent them from growing. Radiation therapy may be recommended after surgery when the surgical margins (the edges of removed tissue) contain cancer cells or when the tumor showed significant nerve involvement. Because completely removing desmoplastic melanoma with clear margins can be challenging, especially on the head and neck, radiation therapy serves as an additional safeguard against cancer recurrence. It is typically delivered over several weeks in daily treatment sessions, with each session lasting only a few minutes.^[2]

For patients who cannot undergo surgery due to the tumor’s location, size, or the patient’s overall health, radiation therapy may serve as the primary treatment. While surgery remains the preferred approach when possible, radiation can effectively control localized desmoplastic melanoma in situations where surgery would cause unacceptable loss of function or appearance. The radiation oncology team carefully plans the treatment to target the tumor while minimizing exposure to surrounding healthy tissues.

Traditional systemic chemotherapy—medications that travel through the bloodstream to reach cancer cells throughout the body—has historically shown limited effectiveness for melanoma compared to other cancer types. These drugs work by interfering with the ability of rapidly dividing cells to grow and multiply. However, melanoma cells have often proven resistant to standard chemotherapy agents. While chemotherapy may occasionally be considered for advanced desmoplastic melanoma that has spread to distant organs, newer treatment approaches have largely replaced chemotherapy as the preferred option for metastatic disease.^[7]

Possible side effects from these standard treatments vary depending on the approach used. Surgery carries risks such as bleeding, infection, wound healing problems, nerve damage (especially relevant for desmoplastic melanoma due to its tendency to involve nerves), scarring, and cosmetic changes. Radiation therapy can cause skin reactions in the treatment area, including redness, irritation, and temporary hair loss. Fatigue is also common during a course of radiation treatment. Long-term effects may include skin texture changes and, rarely, damage to nearby structures. When chemotherapy is used, side effects typically include nausea, hair loss, fatigue, increased infection risk due to low blood cell counts, and other effects that depend on the specific drugs administered.

Innovative Approaches in Clinical Research

Clinical trials investigating new treatments for desmoplastic melanoma have generated considerable excitement in the medical community. These studies have revealed that this particular melanoma subtype may respond exceptionally well to a type of treatment called immunotherapy, which works by helping the patient’s own immune system recognize and attack cancer cells. Unlike traditional treatments that directly target cancer cells, immunotherapy empowers the body’s natural defenses to fight the disease.

The remarkable responsiveness of desmoplastic melanoma to immunotherapy relates to its unique biological characteristics. This cancer type carries an unusually high number of genetic mutations compared to other melanomas. These mutations occur because desmoplastic melanoma develops in skin that has sustained extensive damage from ultraviolet radiation over many years. Each mutation can produce abnormal proteins that the immune system can potentially recognize as foreign invaders. When properly stimulated with immunotherapy drugs, the immune system can mount a powerful attack against cells bearing these abnormal proteins.^[4][6]

The most extensively studied immunotherapy approach for desmoplastic melanoma involves drugs called immune checkpoint inhibitors. These medications work by blocking proteins that normally prevent the immune system from attacking the body’s own cells. Cancer cells cleverly exploit these checkpoint proteins to hide from immune surveillance. By blocking checkpoints like PD-1 (programmed death protein 1), checkpoint inhibitors essentially remove the brakes from the immune system, allowing it to recognize and destroy cancer cells.

Pembrolizumab, marketed under the brand name Keytruda, is a PD-1 checkpoint inhibitor that has shown particularly impressive results in clinical trials for desmoplastic melanoma. A Phase II clinical trial called S1512, conducted by the SWOG Cancer Research Network with funding from the National Cancer Institute and pharmaceutical company Merck, tested pembrolizumab in patients with desmoplastic melanoma in two different clinical situations.^[4][6]

In the portion of the trial involving patients whose desmoplastic melanoma could not be removed with surgery (either because it had spread to distant parts of the body or because its location made surgery impossible), the results exceeded expectations. Among 27 patients who received pembrolizumab, an extraordinary 89% experienced tumor shrinkage—a response rate much higher than typically seen with cancer treatments. Even more remarkably, 33% of patients achieved complete responses, meaning that after treatment, doctors could find no evidence of cancer remaining in their bodies. Another 55% experienced partial responses, with their tumors shrinking substantially though not disappearing completely.^[4][6][11]

Pembrolizumab is administered as an intravenous infusion, meaning it is given through a vein, typically every three weeks. Each infusion session takes about 30 minutes. Treatment generally continues for up to two years, though the exact duration depends on how the cancer responds and whether the patient experiences significant side effects. Some patients may stop treatment earlier if their cancer disappears completely or if side effects become too severe. Conversely, treatment might continue beyond two years in certain circumstances if the medical team believes it remains beneficial.^[11]

Another part of the S1512 trial investigated using pembrolizumab before surgery—an approach called neoadjuvant therapy. The idea behind neoadjuvant treatment is to shrink the tumor before surgical removal, potentially making the operation easier and less extensive. This approach also allows doctors to observe how well the cancer responds to immunotherapy, which provides valuable information about prognosis. Results from this portion of the study, which included patients whose desmoplastic melanoma could be surgically removed, have also been encouraging, suggesting that neoadjuvant pembrolizumab may benefit certain patients.^[4][6]

Other immunotherapy drugs have also been studied in desmoplastic melanoma, though not always in dedicated clinical trials focused exclusively on this subtype. Nivolumab (marketed as Opdivo) is another PD-1 checkpoint inhibitor similar to pembrolizumab. Retrospective studies—which look back at patients who previously received treatment—have suggested that nivolumab also produces good responses in desmoplastic melanoma. Some patients receive nivolumab as an alternative to pembrolizumab, particularly if insurance coverage or other factors make one drug more accessible than the other.^[4][6]

Combination immunotherapy approaches have been approved for treating metastatic melanoma in general. These include nivolumab combined with ipilimumab (Yervoy), which blocks a different checkpoint protein called CTLA-4, and a newer combination of nivolumab with relatlimab (marketed together as Opdualag), which blocks a checkpoint called LAG-3. However, experts now believe that these combinations may not be necessary for desmoplastic melanoma. Since single-agent pembrolizumab or nivolumab already produces such high response rates in this disease, adding additional immunotherapy drugs would expose patients to increased side effects without clear additional benefit. Combination immunotherapy causes more severe immune-related side effects than single-agent treatment.^[4][6]

The side effects of checkpoint inhibitor immunotherapy differ from those of chemotherapy. Because these drugs enhance the immune system’s activity, they can sometimes cause the immune system to attack normal body tissues, resulting in immune-related adverse events. These can affect virtually any organ system. Common immune-related side effects include fatigue, skin rashes, diarrhea and inflammation of the intestines (colitis), and inflammation of hormone-producing glands such as the thyroid or pituitary. More serious but less common complications can involve the lungs (pneumonitis), liver (hepatitis), nervous system, or heart. Many of these side effects can be managed with medications that suppress the immune system, such as corticosteroids, though this sometimes requires stopping immunotherapy treatment temporarily or permanently.

Beyond immunotherapy, researchers are investigating other potential treatment approaches for desmoplastic melanoma. Studies have examined the genetic mutations present in these tumors to identify potential targets for targeted therapy drugs. Comprehensive genomic profiling of desmoplastic melanoma samples has revealed that these tumors carry an average of 77 mutations per megabase of DNA—more than twice the number found in other melanoma types. This extremely high tumor mutational burden explains the strong response to immunotherapy, as more mutations mean more abnormal proteins for the immune system to recognize.^[7]

Some desmoplastic melanomas carry mutations in genes that could potentially be targeted with specific drugs. However, the pattern of mutations in desmoplastic melanoma differs somewhat from other melanomas. For instance, mutations in the BRAF gene, which occur in about half of typical melanomas and can be targeted with BRAF inhibitor drugs, appear less frequently in desmoplastic melanoma. When such targetable mutations are found, patients might be offered participation in clinical trials testing relevant targeted therapy drugs, either alone or in combination with immunotherapy.^[7]

Clinical trials for desmoplastic melanoma are conducted at specialized cancer centers, often in the United States and other countries with advanced research programs. Patients interested in participating in clinical trials should discuss this option with their oncologist, who can help determine whether any appropriate trials are available and whether the patient meets the eligibility criteria. Participation in clinical trials not only provides access to potentially beneficial new treatments but also contributes to advancing medical knowledge that will help future patients with this rare disease.

Most Common Treatment Methods

• Surgical Treatment
  • Wide excision surgery to remove the tumor with surrounding margins of normal tissue
  • Sentinel lymph node biopsy to check for cancer spread to lymph nodes
  • Reconstructive surgery when needed after tumor removal, especially for head and neck locations
• Radiation Therapy
  • Post-surgical radiation when surgical margins contain cancer cells or tumor showed nerve involvement
  • Primary radiation therapy for inoperable tumors due to location or patient health status
  • Delivered over several weeks in daily treatment sessions
• Immunotherapy
  • Pembrolizumab (Keytruda), a PD-1 checkpoint inhibitor, showing 89% response rate in clinical trials for inoperable disease
  • Nivolumab (Opdivo), another PD-1 checkpoint inhibitor with similar mechanism
  • Administered as intravenous infusions every three weeks, typically for up to two years
  • Works by removing immune system brakes, allowing recognition and destruction of cancer cells
  • Neoadjuvant pembrolizumab before surgery to shrink tumors and make operations less extensive
• Combination Approaches
  • Nivolumab plus ipilimumab (Yervoy) combination therapy, though may not be necessary for desmoplastic melanoma given high single-agent response rates
  • Nivolumab plus relatlimab (Opdualag), blocking multiple checkpoint proteins, though associated with increased toxicity
• Targeted Therapy (Investigational)
  • Being explored for patients whose tumors carry specific targetable genetic mutations
  • Tested in clinical trials, sometimes in combination with immunotherapy