Chronic Scar Keratosis

Clinical Features and Pathology

Causes and Risk Factors

• Chronic scars that set the stage:
  • Post-burn scars: the most common cause, accounting for more than 70% of Marjolin transformations.
  • Pressure ulcers and chronic venous stasis ulcers: wounds that have failed to heal for years.
  • Sinus tracts from chronic osteomyelitis.
  • Contracture scars from accidents, war injuries or past surgery.
• How scars become carcinogenic:
  • Chronic inflammation and oxidative stress: inflammatory cytokines (TNF-alpha, IL-6, TGF-beta) and reactive oxygen species are constantly present in the scar, driving an endless cycle of micro-injury and repair that raises the odds of random mutations in keratinocytes.
  • Mutations in the tumor suppressor gene TP53: constant compensatory proliferation of keratinocytes in a poorly nourished environment leads to accumulating mutations in TP53 and CDKN2A.
  • Loss of immune and vascular support (an immunologically privileged site): scar tissue is densely fibrotic and lacks a normal network of blood and lymphatic vessels. This keeps immune surveillance cells (T lymphocytes, Langerhans cells) from reaching and destroying newly abnormal keratinocytes.
  • Micro-trauma and mechanical stress: contracture scars over moving joints (elbows, knees, ankles) crack and bleed again and again, pushing mutated basal keratinocytes to proliferate in a disorganized way.

Clinical Presentation

Lesions appear after a latent period averaging 10–30 years (shorter in older patients and longer in scars from childhood burns):

• What chronic scar keratosis looks like:
  • It arises directly on the surface or along the edge of a hardened or contracted scar band.
  • It forms thick, scaly papules, plaques or nodules that are pale gray, dark brown or skin-colored.
  • The surface is rough, cracked and lumpy, cauliflower-like or wart-like (verrucous/hyperkeratotic).
  • The surrounding scar is usually hard and inelastic, with no hair or sebaceous glands.
• Warning signs of transformation into Marjolin's ulcer:
  • The keratotic plaque thickens quickly and its center breaks down into an ulcer with raised, rolled, everted edges.
  • A characteristic foul smell develops from necrosis and secondary infection.
  • The ulcer oozes blood after minor knocks, and its hard base extends deep into the subcutaneous tissue or bone.

Histopathology

• Massive hyperkeratosis and acanthosis:
  • A very thick overlying stratum corneum, with columns of parakeratosis alternating with orthokeratosis.
  • Enlarged, elongated rete ridges that push deep into the underlying dermal scar.
• Keratinocyte dysplasia:
  • Keratinocytes in the basal and spinous layers completely lose their polarity, with atypical, hyperchromatic nuclei and a high nuclear-to-cytoplasmic (N/C) ratio.
  • Numerous atypical mitoses and dyskeratotic cells.
• Dermal scar background:
  • Dense, fibrotic dermal collagen bundles arranged in parallel without normal architecture.
  • Sparse dermal vessels with thickened, sclerotic walls, and no skin appendages (hair follicles, sebaceous glands).

Differential Diagnosis and Immunohistochemistry (IHC)

Our Approach to Chronic Scar Keratosis

Because of the risk of progression to aggressive Marjolin's ulcer, Haute-Derma manages chronic scar keratosis proactively:

• Never Ignore Any Change on an Old Scar: any new keratotic, cracked or raised lesion on a burn or injury scar more than 10 years old must be biopsied without delay.
• Margin-Controlled Excision and Tissue Reconstruction First: the dysplastic skin is removed completely with a safety margin, combined with skin flaps or skin grafts to release scar tension.
• Regular Dermoscopy Screening for Patients With Extensive Burn Scars: we keep a monitoring record of warning signs of malignant change for every chronic scar area.

How We Diagnose Chronic Scar Keratosis at Haute-Derma

• Detailed Scar History: when the burn, injury or surgery happened, how the wound healed (whether it became infected or stayed ulcerated for a long time), and when the keratotic lesion first appeared.
• High-Resolution Dermoscopy:
  • Scar background: pale white structureless areas with no follicular openings.
  • Scar keratosis: white-gray scale, pale yellow areas, and irregular dotted vessels or hairpin vessels that suggest a risk of malignant transformation.
• Deep Wedge Biopsy: the biopsy must go through the dysplastic epidermis down into the dermal scar (especially at the junction between healthy skin and the keratotic scar) so that invasive squamous cell carcinoma (Marjolin's ulcer) is not missed.
• Immunohistochemistry (p53, Ki-67, p63, p40): confirms the degree of dysplasia and assesses any microinvasion through the basement membrane.

Specialized Treatments at Haute-Derma

• Mohs Micrographic Surgery / Wide Excision:
  • This is the gold standard for chronic scar keratosis at high risk of malignant change. The lesion is excised with 5–10 mm clinical margins.
  • 100% of the surgical margin is checked on frozen sections during the operation to make sure every dysplastic cell has been removed before the wound is closed or grafted.
• UltraPulse CO2 Laser Ablation: an option for extensive scar keratosis with superficial dysplasia, where wide excision could cause serious disfigurement or functional contracture. The UltraPulse CO2 laser removes the dysplastic epidermis precisely, layer by layer, without increasing the risk of scar tissue necrosis.
• Scar Contracture Release and Grafting: alongside removal of the keratosis, a plastic surgeon releases the contracted scar band and places a split-thickness skin graft or free flap to give the area a better blood supply.
• Field Therapy: 5-fluorouracil (5-FU) or imiquimod cream, used under close medical supervision, for extensive superficial keratoses that cannot be operated on right away.