Squamous Cell Carcinoma

Overview – Squamous Cell Carcinoma

Squamous cell carcinoma (SCC) is the second most common type of skin cancer, typically arising in sun-exposed areas. It is a malignant neoplasm of keratinocytes and is associated with ultraviolet radiation, industrial carcinogens, and tobacco exposure. Unlike basal cell carcinoma, SCC can metastasise if untreated. Prompt recognition and management are essential to reduce morbidity and prevent spread.

Definition

Squamous cell carcinoma is a malignant tumour of keratinising squamous epithelial cells, often linked to chronic sun exposure and environmental carcinogens. It commonly presents as a scaly, ulcerating lesion that may rapidly grow and invade surrounding tissue.

Aetiology

• Chronic sun damage (UV exposure)
• Industrial carcinogens (e.g. arsenic, tar, soot)
• Tobacco use
• Immunosuppression (e.g. organ transplant recipients)
• Chronic inflammation or ulcers
• Human papillomavirus (HPV), especially in mucosal lesions

Pathogenesis

• Prolonged exposure to carcinogenic stimuli (e.g. UV light)
  → DNA mutations in squamous keratinocytes
  → Dysplastic changes in the epithelium
  → Progression to invasive neoplasia
• Mutation-driven proliferation and loss of normal differentiation

Morphology

Gross

• Tender papule or nodule
• Rough, hyperkeratotic surface with adherent scale
• Often ulcerated or crusted centre
• May have an erythematous base
• Commonly affects sun-exposed areas, lips, ears, and mucosa

Microscopy

• Pleomorphic squamous cells with increased keratin production (dyskeratosis)
• Keratin pearls: concentric layers of abnormal keratinisation
• Whorls, nests, or sheets of malignant cells
• Abundant pink cytoplasm due to high keratin content
• Invasive growth into dermis or deeper structures

Clinical Features

• Second most common skin cancer after BCC
• May arise from precursor lesions like actinic keratosis
• Rapidly growing, sometimes painful lesion
• May ulcerate, bleed, or crust
• Higher metastatic potential than BCC
• Lymphadenopathy may be present in advanced disease

Management

• Wide surgical excision: gold standard
• Cryotherapy: for superficial or small lesions
• Adjuvant radiotherapy: for high-risk, incompletely excised, or inoperable cases
• Follow-up: due to risk of recurrence or metastasis, particularly in high-risk patients

Summary – Squamous Cell Carcinoma

Squamous cell carcinoma is a malignant skin tumour of squamous keratinocytes, most commonly caused by UV damage and carcinogen exposure. It often presents as a scaly, ulcerated lesion on sun-exposed skin and requires early, wide excision to prevent local invasion or metastasis. For more information, visit our Skin & Dermatology Overview page.