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This is a clinician-written, evidence-based summary aligned to the 2026 MLA Content Map. It is intended for medical students and junior doctors preparing for the UKMLA. Always cross-reference with NICE guidance, local protocols, and clinical judgement.
Key points
- CAN metastasise (~2-5% overall; higher for lip, ear, immunosuppressed)
- Firm, irregular, keratotic, ulcerated nodule on sun-exposed skin
- Pre-malignant precursors: actinic keratoses and Bowen's disease (SCC in situ)
- Surgical excision with >=5 mm margin. Mohs for high-risk
- Immunosuppressed patients (transplant recipients) have massively increased risk
Overview
Cutaneous SCC is a malignant tumour of epidermal keratinocytes. Unlike BCC, SCC can metastasise (predominantly lymphatic to regional nodes). Risk ~2-5% overall but 10-15% for lip lesions and much higher in immunosuppressed patients. Can arise de novo or from actinic keratoses (5-10% lifetime transformation risk) or Bowen's disease (SCC in situ, 3-5% progression).
Epidemiology
Over 30,000 cases/year in the UK. Peak over age 70. Risk factors: cumulative UV, immunosuppression (transplant recipients 65-250x risk), HPV, chronic wounds (Marjolin's ulcer), previous radiotherapy, arsenic exposure.
Clinical Features
Symptoms
Non-healing, growing, keratotic nodule or ulcer on sun-exposed skin
May be painful or tender (unlike BCC)
Rapidly growing dome-shaped nodule with central keratin plug (keratoacanthoma)
Signs
Firm, irregular, flesh-coloured to erythematous nodule with keratotic surface
Ulceration with everted edges
Background sun-damaged skin with actinic keratoses
Regional lymphadenopathy (metastasis)
Investigations
First-line
Excision biopsyPreferred — diagnostic and therapeutic
DermoscopyWhite structureless areas, keratin, polymorphous vessels
Second-line
Lymph node assessmentClinical palpation; ultrasound + FNAC if palpable nodes
Specialist
CT/MRIIf deep invasion or perineural spread suspected
Management
BAD Guidelines on SCC + NICE CKS1
Referral
- Two-week wait referral for any suspicious keratotic nodule/ulcer
2
Surgical excision
- Minimum 5 mm margin for low-risk SCC
- High-risk (>2 cm, >4 mm depth, lip/ear, immunosuppressed): wider margins or Mohs
3
Pre-malignant lesion management
- Actinic keratoses: topical 5-FU, imiquimod, cryotherapy, PDT
- Bowen's disease (SCC in situ): topical 5-FU, cryotherapy, PDT, or excision
Complications
- Metastasis: ~2-5% overall; higher for lip, ear, immunosuppressed
- Local recurrence: ~5-8% after excision
- Perineural invasion: Pain, paraesthesia — poor prognostic factor
UKMLA Exam Tips
- 1SCC = keratotic nodule + potential to metastasise. BCC = pearly, rolled, almost never metastasises
- 2Marjolin's ulcer: SCC arising in a chronic wound/burn scar
- 3Actinic keratosis to SCC is the key pre-malignant pathway
- 4Bowen's disease = SCC in situ — red, scaly, well-demarcated patch
- 5Immunosuppressed patients need regular skin surveillance
- 6Keratoacanthoma: rapidly growing dome + keratin plug — treat as SCC
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