What Is Squamous Cell Carcinoma?

Squamous cell carcinoma (SCC) is the second most common form of skin cancer, arising from the keratinocytes of the epidermis. Unlike basal cell carcinoma, SCC carries a genuine, if generally small, risk of spreading to lymph nodes or beyond, which makes prompt diagnosis and treatment more important. Most SCCs are cured with appropriate treatment, particularly when caught early.

Causes & Risk Factors

Cumulative UV exposure — the leading cause, particularly in fair-skinned individuals with a history of sun exposure or sunbed use
Immunosuppression — a significantly increased risk in organ transplant recipients and others on long-term immunosuppressive treatment
Pre-existing actinic keratosis or Bowen's disease, which can progress to invasive SCC if untreated
Chronic wounds, long-standing scars or areas of chronic inflammation (a rare but recognised cause, sometimes called a Marjolin's ulcer)
Smoking, and in some cases HPV infection (particularly for genital or periungual lesions)

Signs to Look For

A firm, red, scaly or crusted lump or plaque, often tender to touch
A sore that does not heal, or a wart-like growth that bleeds or crusts
Rapid growth over weeks to a few months
A lesion arising within a long-standing scar, ulcer, or area of actinic keratosis

NICE Referral Pathway

Suspected SCC should be referred urgently. Under NICE guideline NG12, a suspicious lesion consistent with SCC should be seen on the 2-week-wait urgent suspected cancer pathway, allowing prompt biopsy, diagnosis and treatment planning.

Diagnosis & Risk Stratification

Diagnosis is confirmed by biopsy. SCCs are then stratified into lower-risk and higher-risk categories based on features including size (over 20mm), depth of invasion, degree of differentiation, location (ear and lip carry higher risk), perineural invasion, and whether the patient is immunosuppressed. This risk stratification guides both the surgical margin required and the intensity of follow-up.

Treatment Options

Surgical excision — the standard treatment, with margins of around 4mm for low-risk lesions and 6mm or more for high-risk lesions, followed by direct closure or reconstruction depending on the defect
Mohs micrographic surgery — used for high-risk lesions, recurrent SCC, or cosmetically and functionally sensitive sites, confirming complete margin clearance while preserving healthy tissue
Radiotherapy — used where surgery is not suitable, or as adjuvant treatment after surgery for selected high-risk features (such as perineural invasion)
Sentinel lymph node biopsy and staging imaging — considered for higher-risk SCCs, to assess whether the cancer has spread to nearby lymph nodes

Follow-Up

Because SCC carries a risk of local recurrence and, in a minority of higher-risk cases, spread to lymph nodes, regular follow-up is recommended after treatment, with the frequency and duration tailored to the individual risk category of the lesion.

Squamous Cell Carcinoma (SCC)