A scar is the body’s natural result of healing, where fibrous tissue replaces the normal skin structure following an injury, surgery, or burn. This tissue often appears different from the surrounding skin, being thicker, less flexible, and sometimes discolored. While the vast majority of scars remain benign, a very rare form of skin cancer can potentially develop within long-standing scar tissue. This malignant change is not a concern for a new, well-healed surgical incision, but rather an uncommon complication associated with chronic, unstable, or previously traumatized areas of skin.
The Specific Link Between Scars and Cancer
The malignant degeneration of a scar or chronic non-healing wound is a documented phenomenon, most often classified as Marjolin’s Ulcer. This condition is a rare but aggressive form of cutaneous cancer. Squamous Cell Carcinoma (SCC) is the most frequently identified type, accounting for 80% to 90% of cases. The development of this cancer is fundamentally linked to chronic inflammation and tissue instability that persists long after the initial injury has seemingly healed.
Scar tissue, particularly in old, unstable wounds, lacks the normal blood and lymphatic vessel networks found in healthy skin. This poor vascularization creates an environment where the local immune system struggles to function effectively, making the area an “immune-privileged site.” Cancerous cells that spontaneously arise are protected from the body’s immune surveillance, allowing them to grow and spread undetected.
Chronic irritation, repeated minor trauma, and persistent inflammation within the compromised tissue further drive the malignant process. This ongoing cellular stress leads to repeated cycles of cell proliferation and repair, increasing the likelihood of spontaneous DNA mutations that result in cancer. The latency period between the initial injury and the diagnosis of cancer is often substantial, averaging around 30 to 35 years, though it can range from less than a year to over 70 years.
The cancerous transformation usually manifests as a non-healing ulcer that develops within the scar and grows progressively larger. The aggressive nature of Marjolin’s Ulcer means it has a higher rate of regional metastasis compared to typical, spontaneously occurring SCCs. The underlying mechanism is a complex interplay of chronic cellular damage, impaired delivery of immune cells, and genetic instability within the scar tissue itself.
Types of Scars That Carry Risk
While any scar or chronic wound can theoretically undergo malignant transformation, the risk is not uniform across all types of skin injury. The highest documented risk is associated with chronic burn scars, particularly those that were severe, covered a large area, or healed slowly by secondary intention (without surgical closure). Approximately 2% of burn scars may eventually undergo this malignant change.
Scars resulting from other sources of chronic skin damage also carry a recognized, though lower, risk. These include chronic pressure ulcers (bedsores) and long-standing venous ulcers, which develop due to poor blood circulation in the legs. Traumatic scars subject to repeated breakdown or irritation, as well as scars resulting from chronic osteomyelitis (bone infection), have also been implicated.
Scars that have been exposed to radiation treatment represent another high-risk category due to the lasting tissue damage caused by the treatment. In contrast, common surgical scars, keloids (scars that grow beyond the original wound boundary), and hypertrophic scars (raised scars that stay within the wound boundary) are considered very low risk. These common scars only become a concern if they become chronically irritated, repeatedly break down, or fail to heal over a very long period.
Recognizing Changes in Scar Tissue
The most important step for anyone with a long-standing scar is regular self-examination, especially for those with high-risk scars like old burn injuries. Malignant change should be suspected if a scar develops a new, open sore that does not heal within a few weeks or months. This persistent, non-healing ulceration is often the first and most recognizable sign of a problem.
Other changes that warrant immediate attention include rapid or noticeable growth in the size or thickness of the scar, which may present as a lump or nodule beneath the surface. The scar may also develop elevated, rolled margins around a central ulceration, a characteristic feature of an aggressive lesion. Changes in the scar’s texture, such as becoming hardened, scaly, or crusty, are also concerning signs.
A malignant ulcer may also exhibit bleeding that occurs easily with minor contact, or a persistent, foul-smelling discharge not typical of a healing wound. Additionally, the onset of severe or persistent pain in a scar that was previously pain-free should be evaluated by a healthcare professional. If any of these warning signs appear, a physician will perform a biopsy, which involves taking a small tissue sample to be examined under a microscope, to confirm the presence of cancer cells and guide treatment.