Discoid lupus erythematosus-associated SCC

Background — DLE

• Discoid lupus erythematosus is the commonest form of chronic cutaneous lupus, characterised by scarring, atrophic, hyperkeratotic plaques with follicular plugging on sun-exposed skin (face, scalp, ears).
• Subset of patients also have systemic lupus erythematosus; most do not.
• Long-term complications: scarring alopecia, dyspigmentation, atrophy and — in chronic active disease — squamous cell carcinoma.

Risk & pathogenesis

• Lifetime cSCC risk in chronic DLE — 3–5%; substantially higher in long-standing scalp and lip disease.
• Latency typically 10–30 years from DLE onset to SCC diagnosis.
• Risk factors:
  • Long disease duration.
  • Scalp and lower-lip involvement (commonest sites of cSCC).
  • Inadequate sun protection and ongoing photodamage.
  • Smoking — especially for lip cSCC.
  • Skin of colour — disproportionate burden.
  • Poor inflammatory control with persistent active disease.
• Mechanism — chronic inflammation, repeated cycles of ulceration and re-epithelialisation, scarring with disordered cellular kinetics, loss of dermal immunosurveillance, photodamage of atrophic skin.

Clinical features

• New non-healing ulcer, exophytic mass, induration, increased hyperkeratosis or rapidly enlarging nodule within an established DLE plaque.
• Most common sites — scalp (especially in patients with scarring alopecia areas), lower lip (often combined with smoking and chronic UV exposure), face and ears.
• Often misattributed to a "DLE flare" — diagnostic delay common.
• Regional lymphadenopathy at presentation in a substantial proportion.
• Differential — well-differentiated cSCC arising in actinic skin (less context for misdiagnosis); keratoacanthoma; chronic non-healing ulcer; basal cell carcinoma; deep fungal infection.

Management

• Multiple deep biopsies of any change in a chronic DLE plaque.
• Wide local excision with at least 1 cm margins; Mohs micrographic surgery for facial / lip / functionally important sites.
• Imaging staging — CT chest/abdomen/pelvis ± MRI of the affected region.
• Sentinel lymph node biopsy / regional nodal assessment given high occult nodal disease rate (20–40%).
• Adjuvant radiotherapy for incomplete margins, perineural invasion, multiple positive nodes or ENE.
• Cemiplimab (NICE TA802) for advanced / metastatic disease unsuitable for surgery / RT — caution in active autoimmune disease (potential to flare DLE / SLE).
• Optimised long-term DLE control — topical / intralesional steroids, calcineurin inhibitors, hydroxychloroquine, mycophenolate, methotrexate; rigorous photoprotection; smoking cessation.

Prognosis & surveillance

5-year overall survival 50–70% — worse than conventional cSCC. Adverse factors: scalp and lip site, large tumour size, perineural / lymphovascular invasion, nodal metastasis, late presentation, immunosuppressive therapy. Lifelong surveillance of patients with chronic DLE is essential — counsel patients to flag any new ulcer, induration or change in chronic plaques. Excellent inflammatory control plus rigorous photoprotection are the key preventive measures.