Squamous Cell Carcinoma (SCC)

What Is Squamous Cell Carcinoma?

Squamous cell carcinoma (SCC) is a skin cancer that arises from squamous cells. The flat cells that make up the middle and outer layers of the skin. It is the second most common skin cancer worldwide, after basal cell carcinoma. SCC can develop on any part of the body, but most often appears on areas with high sun exposure such as the face, ears, lips, scalp, neck, hands, and arms. Unlike BCC, SCC has a real. Though still relatively low. Risk of spreading (metastasizing) to lymph nodes and distant organs, especially when the tumor is large, deep, or in a high-risk location.

Risk Factors

Many of the same factors that cause BCC also contribute to SCC, but SCC has additional unique risk factors:

• Cumulative UV radiation exposure. The most important risk factor; sun damage accumulates over a lifetime
• History of actinic keratoses (see below). These pre-cancerous lesions are direct precursors
• Immunosuppression. Transplant patients, those on immunosuppressive drugs, or people with HIV are at dramatically higher risk and develop more aggressive SCCs
• Human papillomavirus (HPV) infection. Certain HPV strains are strongly linked to SCC on the genitals, perianal area, and nail unit
• Chronic non-healing wounds, burn scars, or ulcers. SCC developing in a scar is called Marjolin's ulcer and is particularly aggressive
• Prior radiation therapy to the skin
• Exposure to arsenic, industrial chemicals, or polycyclic aromatic hydrocarbons
• Fair skin, light hair, and light eyes
• Personal or family history of skin cancer
• Tobacco use. Associated with SCC of the lip
• Xeroderma pigmentosum or other rare DNA repair disorders

How Does SCC Look?

SCC can appear in many forms. Being aware of these signs helps with early detection:

• A firm, red nodule. Often with a rough, scaly, or crusted surface
• A flat sore with a scaly crust that does not heal or keeps returning
• A new sore or raised area on an old scar
• A rough, wart-like growth on the lip, inside the mouth, or on the genitals
• A red sore or rough patch inside the mouth
• A non-healing sore or new growth on or near a mole or existing skin lesion
• Tenderness, pain, or numbness around a skin lesion. A warning sign of nerve involvement
• SCCs on the lip or ear carry higher risk of spreading and should be evaluated promptly

Actinic Keratosis: The Precursor

Actinic keratoses (AKs) are rough, scaly patches caused by years of sun damage. They are not yet cancer, but they are the most common precursor to SCC. Understanding AKs is important for prevention:

• AKs appear as dry, rough, scaly patches 2–6 mm in size, often on the face, scalp, ears, neck, and hands
• They may be pink, red, or brown, and may itch, burn, or feel tender
• Left untreated, approximately 5–10% of AKs may eventually develop into SCC. But it is impossible to predict which ones
• Patients with many AKs (field cancerization) are at significantly higher risk for SCC
• AKs are treated with cryotherapy, topical creams (5-fluorouracil, imiquimod, diclofenac), photodynamic therapy, or laser resurfacing
• Treating AKs reduces. But does not eliminate. The risk of developing SCC

SCC In Situ (Bowen's Disease)

SCC in situ, also called Bowen's disease, is an early form of SCC where abnormal cells are confined entirely to the outer layer of skin (epidermis) and have not yet invaded deeper layers. It is important to understand:

• SCC in situ appears as a persistent, slowly enlarging red, scaly patch. It can look like a stubborn eczema or psoriasis plaque
• It is not invasive cancer yet, but it should be treated because it can progress to invasive SCC over time
• Treatment options include topical therapy (5-fluorouracil cream, imiquimod), cryotherapy, photodynamic therapy, curettage, or surgical excision
• Mohs surgery may be recommended for SCC in situ with an invasive component or in high-risk locations
• Bowenoid papulosis is an HPV-associated variant occurring on the genitals that also requires treatment

Treatment

Treatment choice depends on the SCC's size, depth, location, histologic grade, and your overall health.

• Mohs Micrographic Surgery. Recommended for high-risk SCCs: those in H-zone locations (nose, ears, lips, eyelids), recurrent tumors, poorly defined borders, perineural invasion, or in immunosuppressed patients. Provides real-time complete margin assessment and the highest cure rate (approximately 97% for primary SCC).
• Standard Excision. Appropriate for low-risk SCCs on the trunk and extremities; recommended margins are 4–6 mm for well-defined low-risk tumors and up to 10 mm for high-risk lesions.
• Electrodessication and Curettage (ED&C). Suitable for small, well-differentiated, superficial SCCs in low-risk locations only. Not appropriate for high-risk features or the face.
• Radiation Therapy. Used when surgery is not possible, as adjuvant therapy after surgery for high-risk features, or to treat the lymph node region in high-risk cases.
• Systemic Therapy. For locally advanced or metastatic SCC, options include cemiplimab (immunotherapy/PD-1 inhibitor) or platinum-based chemotherapy. These are decided by an oncology team.
• Sentinel Lymph Node Biopsy. May be considered for high-risk SCCs to check whether cancer cells have spread to nearby lymph nodes.

Follow-Up Schedule

After treatment, regular monitoring is essential because SCC has a real risk of local recurrence and metastasis, and patients often develop new primary skin cancers.

• First 2 years: full-body skin exam every 3 to 6 months, with lymph node palpation at each visit
• Years 3 to 5: exam every 6 to 12 months depending on your risk level
• After 5 years: annual exams are recommended for life. Skin cancer risk remains elevated permanently
• High-risk patients (immunosuppressed, multiple SCCs, perineural invasion): every 3 months for the first 2 years
• Imaging studies (CT, PET-CT, ultrasound) may be ordered for high-risk SCCs to check for lymph node or distant spread
• Self-examination of the skin and lymph nodes should be performed monthly at home
• Report any new lumps, bumps, or skin changes to your dermatologist promptly. Do not wait for your next scheduled appointment
• Sun protection must be maintained lifelong. Additional sun exposure continues to drive new tumors