Cutaneous Squamous Cell Carcinoma: Clinical Overview
Cutaneous squamous cell carcinoma (cSCC) is the second most common skin cancer, arising from epidermal keratinocytes, with cumulative sun exposure being the most critical risk factor, particularly in fair-skinned individuals. 1
Epidemiology and Incidence
cSCC represents a significant and growing health burden:
- Lifetime risk: 9-14% for men, 4-9% for women in the United States 1
- Annual incidence: 200,000-400,000 new cases in the U.S., with over 3,000 disease-related deaths annually 1
- Increasing incidence: More than 200% increase documented from 1960 to 2000, with continued upward trends 1
The rising incidence reflects both increased sun exposure patterns and improved detection, making this a growing clinical concern.
Risk Factors
Primary Risk Factors
The most important risk factors include:
- Cumulative UV exposure: Especially during childhood and youth—this is the single most important modifiable risk factor 1
- Fair skin: Highest risk population, though patients with skin of color are also susceptible 1
- Immunosuppression: Increasingly recognized as a major contributor, particularly in organ transplant recipients 1
- Chronic inflammation: Areas of burns, scars, or chronic wounds 1
- Ionizing radiation exposure 2
- Chemical exposures: Arsenic and industrial chemicals 2
Important Clinical Caveat
While fair-skinned individuals on sun-exposed areas represent the classic presentation, awareness is growing that patients with darker skin types develop cSCC in sun-protected sites or areas of chronic inflammation 1. This can lead to delayed diagnosis if clinicians maintain too narrow a clinical suspicion.
Clinical Presentation
Anatomic Distribution
In fair-skinned individuals, sun-exposed areas predominate:
- Head and neck (most common)
- Backs of arms and hands
- Any sun-exposed surface 1
In patients with skin of color:
- May emerge in sun-protected sites
- Areas of chronic inflammation 1
Clinical Appearance
The presentation varies by histological subtype:
- Dry, scaly erythematous patch or plaque
- Firm hyperkeratotic papule, plaque, or nodule
- May present with ulceration 3
cSCC is typically slow-growing but carries metastatic potential if untreated, with approximately 5% of cases metastasizing 4.
Diagnosis
Biopsy Recommendations
The recommended biopsy techniques are punch biopsy, shave biopsy, or excisional biopsy, with technique selection based on lesion characteristics 1:
- Biopsy depth and size must be adequate to provide accurate diagnosis and guide therapy 1
- Repeat biopsy should be considered if initial specimen is inadequate for accurate diagnosis 1
- Modified Breslow measurement should exclude parakeratosis/scale-crust and measure from the base of ulcer if present 1, 5
Critical Information for Pathologist
Provide comprehensive clinical history including:
- Radiation exposure
- Burn history
- Organ transplant status
- Presence of aggressive histologic features
- Perineural or vascular invasion
- Invasion of fascia, muscle, or bone 1
Treatment Approach
Risk Stratification is Essential
Treatment decisions must account for whether the tumor is low-risk or high-risk, as this fundamentally changes management strategy.
Low-Risk Primary cSCC
For low-risk primary cSCC, standard excision with 4-6 mm margins to the depth of mid-subcutaneous adipose tissue with histologic margin assessment is recommended 1:
- Curettage and electrodesiccation (C&E) may be considered for low-risk, primary cSCC in non-terminal hair-bearing locations 1
High-Risk cSCC
Mohs micrographic surgery (MMS) is recommended for high-risk cSCC 1:
This provides the highest cure rates while maximizing tissue preservation. High-risk features include:
- Larger size
- Deeper invasion (>2mm)
- Perineural or vascular involvement
- High-risk anatomic locations (central face, ears, genitalia)
- Aggressive histologic subtypes
- Immunosuppressed patients 4, 6
Strong caution is advised when selecting standard excision for high-risk tumors without complete margin assessment 1.
Non-Surgical Options
When surgery is not feasible or preferred:
- Radiation therapy can be considered for low-risk tumors, though cure rates may be lower 1
- Cryosurgery may be considered for low-risk cSCC when more effective therapies are contraindicated 1
- Topical therapies (imiquimod, 5-FU) and photodynamic therapy are NOT recommended for treatment of invasive cSCC based on available data 1
Advanced Disease Management
For regional lymph node metastases, surgical resection with or without adjuvant radiation therapy and possible systemic therapy is recommended 1:
- Combination chemoradiation for inoperable disease 1
- Epidermal growth factor inhibitors and cisplatin may be considered for metastatic disease 1
- Multidisciplinary consultation is recommended for locoregional or distant metastases, particularly in immunosuppressed patients 1
Treatment Planning Considerations
A treatment plan must consider recurrence rate, preservation of function, patient expectations, and potential adverse effects 1. The goals are cure of the tumor with maximal preservation of function and cosmesis 5.
Important Clinical Nuance
Age alone should not dictate treatment aggressiveness. Healthy nonagenarians deserve treatment with optimal cure rates, while significant medical comorbidities at any age may justify lower-intensity options prioritizing quality of life 1. In select circumstances after careful consideration, observation may be appropriate 1.
Follow-Up Strategy
Surveillance intensity depends on disease extent 5:
Local disease:
- Every 3-6 months for 2 years
- Then every 6-12 months for 3 years
- Then annually for life
Regional disease:
- Every 1-3 months for year 1
- Every 2-4 months for year 2
- Every 4-6 months for years 3-5
- Every 6-12 months thereafter for life
All follow-up should include complete skin and regional lymph node examination 5.
Key Clinical Pitfalls
- Don't underestimate risk in immunosuppressed patients—these individuals have dramatically increased risk and more aggressive disease 1
- Don't assume darker skin protects—cSCC occurs in all skin types, sometimes in atypical locations 1
- Don't use topical therapies for invasive cSCC—these are not recommended despite their use in other contexts 1
- Don't treat high-risk tumors without complete margin assessment—this significantly increases recurrence risk 1