Squamous Cell Carcinoma (SCC) – Metastatic Risk 

SCC is the second most common skin cancer, arising from keratinocytes. It can be locally destructive and has a real, albeit modest, risk of metastasis (unlike BCC).

Core Features / Risk Factors

Demographics:

• Typically age >50; strong risk in fair skin (Fitzpatrick I–II).

UV Exposure:

• Chronic UV exposure (outdoor work, sunbeds).

Chronic Damage:

• Actinic keratoses or Bowen disease (SCC in situ).

• Long-standing scars and burns (Marjolin’s ulcer), chronic leg ulcers, or pre-existing lesions (Lichen Sclerosus, Discoid Lupus).

Immunosuppression:

• Organ transplant, haematological malignancy, HIV, or immunosuppressive drugs 

History Specific to Skin of Colour (SOC)

• SCC is the most common skin cancer in Black individuals and other darker skin types.

• Primary Site: Often arises in non–sun-exposed sites, chronic scars, and ulcers, rather than the classic sun-exposed areas (face, ears).

• Appearance: Described as a "dark bump" or "purple/black crusty patch" rather than the typical "red scaly patch."

• Advanced Disease: Rapid growth, deep pain, or new lump in regional lymph nodes suggests high-risk or advanced disease.

Perform a full-skin and lymph node exam.

• Primary Lesion: 

Classically a scaly, erythematous or hyperkeratotic papule, plaque, or nodule that is indurated (firm/hard) on palpation. May have central ulceration and a firm, raised edge or present as a cutaneous horn.

• Distribution:

  • Lighter Skin: Predominantly sun-exposed sites (Face, ears, scalp, dorsum of hands).

  • Skin of Colour: More often on non–sun-exposed sites (Legs, buttocks, genital/perianal areas) or in chronic scars/ulcers.

• Colour and Cues in SOC:

  • Classic "red, scaly" may be subtle or absent.

  • Lesion may appear hyperpigmented (brown to black) with overlying scale/crust, or purple/violaceous.

  • Look for change in architecture and induration, not just redness.

• High-Risk Features (Worse Prognosis): Size >2 cm, location on the ear, lip, central face, hands, feet, or on long-standing scars/ulcers. Look for perineural symptoms (pain/numbness).

Treatment is highly individualized based on risk, site, and patient factors. Biopsy is always required first.

1. Localized / Low-Risk SCC

• Standard Surgical Excision: First-line for most low-risk tumours. Typical margins are 4–6 mm of normal skin.

• Other Methods (for SCC in situ/Bowen’s): Curettage and electrodessication (ED&C), cryotherapy, or photodynamic therapy (PDT) may be used.

  • SOC Caution: These methods have a higher recurrence risk and pose a high risk of dyspigmentation and scarring to use cautiously.

2. High-Risk or Cosmetically Sensitive Sites

• Mohs Micrographic Surgery: Gold Standard for large, ill-defined, recurrent, or high-risk SCCs (Face, ears, lips, genitalia).

  • Benefit in SOC: Allows complete margin control while sparing tissue, which is crucial for minimizing hypertrophic scarring and pigment change.

3. Advanced Disease / Metastasis

• Nodal Assessment: For clinically high-risk lesions (large, rapid growth, perineural symptoms), evaluation may include ultrasound/CT and fine-needle aspiration (FNA) or sentinel node biopsy.

• Systemic Therapy: For locally advanced or metastatic SCC not amenable to surgery/radiation, Immune Checkpoint Inhibitors (e.g., PD-1 inhibitors like cemiplimab) are now first-line options in the specialist setting.

4. Follow-up and Prevention

• Regular Dermatology Follow-up: At least annually; more frequent (e.g., every 3–6 months) for high-risk patients. Crucial to examine the entire skin, including scars, chronic ulcers, and genital/perianal skin in darker skin types.

• SOC Prevention Emphasis: Counsel patients that SCC can still arise even without severe sunburn history, particularly on scars, legs, and non–sun-exposed areas. Any non-healing ulcer or changing scar/lesion in these areas must be biopsied. 

1. Skinsight – Squamous Cell Carcinoma

2. StatPearls / NCBI Bookshelf – Cutaneous Squamous Cell Carcinoma (Hadian et al., 2024)

3. DermNet NZ – Cutaneous Squamous Cell Carcinoma (Oakley, 2015)