Squamous cell carcinoma is a common variant of skin cancer. Metastases are rare but may occur in 2-5% of patients.

SCC is the proliferation of atypical, transformed keratinocytes in the skin with malignant behaviour. It ranges from in situ tumours (also known as Bowen's disease) to invasive tumours and metastatic disease. Precursor lesions for SCCs are called actinic (or sun-damage) keratosis.

Aetiology:

• More than 90% are associated with DNA mutations
• Mutations in the p53 tumour suppressor gene are caused by exposure to UV radiation

Risk factors:

• excessive exposure to sunlight/UV
  • actinic keratoses and Bowen's disease
• Exposure to ionising radiation
• immunosuppression e.g. following renal transplant, HIV
• Older age
• male sex
• smoking
• long-standing leg ulcers (Marjolin's ulcer)
• genetic conditions e.g. xeroderma pigmentosum

PC

Present as enlarging scaly or crusted lumps - usually arise within pre-existing acitinic keratosis or intraepidermal carcinoma

• Growing tumours - SCC grow over 3 to 6 months (faster then BCC)