Squamous Cell Carcinoma

Malignant tumour that arises from supra-basal keratinocytes

Aetiology

Major Risk Factors

Factor
Role
Chronic UV exposure (UVB)
DNA damage (p53 mutation)
Actinic keratosis
Precancerous lesion
Immunosuppression
Aggressive behavior
Chronic wounds/scars
Marjolin ulcer
Ionizing radiation
Carcinogenesis
HPV infection
Anogenital & periungual SCC
Chemical carcinogens
Arsenic, tar

Pathophysiology

  • UV radiation → DNA damage in keratinocytes
  • Mutation of tumor suppressor genes (p53, NOTCH)
  • Progression:
    • Normal skin → Actinic keratosis → SCC in situ → invasive SCC
  • Failure of immune surveillance enhances tumor progression

Growth and spread

  • Locally invasive
  • Low but definite risk of metastases
    • Poor prognosis once metastatic

Clinical presentation

Typical Lesions

  • Firm, hyperkeratotic papule, plaque, or nodule
  • May ulcerate → crateriform or ulcerative lesion
  • Often erythematous with scale or crust
  • Lesions may be tender or painful
notion image

Common Sites

  • Sun-exposed areas
    • Face
    • Scalp (balding)
    • Ears
    • Dorsum of hands
  • Lips (lower lip)
  • Anogenital region (HPV-related)

Investigations

Histopathology (Gold standard)

  • Invasive cords and nests of atypical squamous cells
  • Keratin pearly horn formation (well-differentiated SCC)
  • Cellular atypia and mitoses
notion image

Grading

Grade
Features
Well-differentiated
Prominent keratinization
Moderately differentiated
Less keratinization
Poorly differentiated
Minimal keratinization, aggressive

Management

  • Usually complete surgical excision (+ biopsy) with a wide margin
  • May be treated topically if smaller and not invasive