Squamous cell skin cancer

Background/Epidemiology

• Tumour originating from the keratinocytes in the skin
• Second most common skin cancer after BCC (accounts for ~20% of non-melanomatous skin cancer)
• Incidence is rising.  Currently around 17 per 100,000 people per year (around 10,000 cases per year)

Risk Factors

• UV exposure
• Immunosuppression
• Exposure to radiation or carcinogens
• HPV infection (warts)
• Fair (type I) skin
• Chronic inflammation
• Development from pre-malignant disease e.g. Bowen’s disease, actinic keratosis

Pathophysiology

• Loss of function mutations in p53 (e.g. caused by UV-light)
• Other genetic neoplastic changes e.g. mutations in BCL2, RAS and eGFR
• Typical histological features include
  • nuclear atypia, frequent mitotic figures, cellular pleomorphism, hyper- and parakeratosis (retaining the nuclei in the stratum corneum), a disorganised progression of cells from basal to apical layers of the epidermis
  • SCC can be graded based on histology as
    • Well differentiated (normal looking nuclei with abundant cytoplasm and extracellular keratin)
    • Moderately differentiated
    • Poorly differentiated (many atypical nuclei and mitotic figures; >nuclear:cytoplasmic ratio; less keratinisation)

Presentation

• Usually on sun-exposed areas e.g. bald scalp, ears, face and hands
• Variable presentation
  • from rapid development of a painful keratotic nodule
    • may be over an area of pre-existing dysplasia
  • to new, erythematous, infiltrated, warty nodule/plaque that can ulcerate
  • Usually, a slowly-growing, tender, scaly/crusted lump

Diagnosis/Management

• Excisional biopsy is the management of choice for most patients
  • As with BCC, Mohs surgery can be considered for tumours that are high risk or those in difficult areas
  • Radiotherapy may be required in unresectable tumours
  • Cryotherapy is an option for small, well-defined and low risk tumours