Cutaneous squamous cell carcinoma !
Squamous cell carcinoma is the second most common skin cancer. It grows on sun-damaged skin, often from rough precancerous spots, and can spread.
Updated 2026-11-01
Structures involved
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In the clinical exam
Why it happens
- Dysplasia and carcinoma in situ
- Invasion and metastasis: the metastatic cascade, step by step
- Differentiation and anaplasia: how a tumour cell looks under the microscope
- Radiation and cancer: ultraviolet and ionizing
- Biopsy: excisional, incisional, core needle, punch and fine-needle aspiration
- Heavy metals: lead, mercury, arsenic and cadmium
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What it is
A malignant tumour of the keratinocytes of the epidermis, usually on chronically sun-exposed skin. It often develops from actinic keratosis and, unlike basal cell carcinoma, can metastasise to regional lymph nodes.
Who gets it
The second most common skin cancer. In Colombia and other Andean countries, intense year-round UV radiation and outdoor farm work make actinic keratoses and squamous cell carcinoma common in older adults; risk is far higher in organ-transplant recipients.
Causes
- Cumulative ultraviolet exposure causing TP53 mutations in keratinocytes
- Progression from actinic keratosis (precursor) or squamous cell carcinoma in situ (Bowen disease)
- Chronic wounds, burn scars and long-standing ulcers (Marjolin ulcer)
- Human papillomavirus, arsenic exposure and ionising radiation
Risk factors
- Fair skin and long-term sun exposure, outdoor work
- Older age and male sex
- Multiple actinic keratoses
- Immunosuppression, especially organ transplant recipients and people living with HIV
- Chronic scars, burns or non-healing wounds
- Smoking (for lip tumours)
Pathophysiology
UV damage produces atypical keratinocytes confined to the lower epidermis (actinic keratosis), which may progress to full-thickness atypia (carcinoma in situ) and then break through the basement membrane into the dermis. Invasive tumours can spread along nerves and to regional lymph nodes, most often in the head and neck.
Classification
- Actinic keratosis: precursor; rough, scaly patch on sun-exposed skin
- Squamous cell carcinoma in situ (Bowen disease)
- Invasive squamous cell carcinoma, well to poorly differentiated
- Keratoacanthoma: rapidly growing crater-shaped variant, usually managed as squamous cell carcinoma
- High-risk features: lip, ear, size over 2 cm, depth, perineural invasion, poor differentiation, immunosuppression
Symptoms and signs
- A firm, scaly or crusted red papule, plaque or nodule on sun-exposed skin (face, ears, scalp, lip, back of the hands)
- A sore that bleeds or ulcerates and does not heal
- A rough, sandpaper-like patch (actinic keratosis) that thickens or becomes tender
- A new lesion or ulcer in an old scar or chronic wound
Diagnosis
- Clinical
- Examination of sun-exposed skin and palpation of regional lymph nodes; dermoscopy helps distinguish it from other lesions.
- Tests
- Skin biopsy reaching the dermis confirms invasion and grade; fine-needle aspiration or biopsy of a suspicious lymph node.
- Imaging
- Ultrasound of regional nodes, and CT or MRI for high-risk tumours or suspected deep or perineural spread.
Differential diagnosis
- Basal cell carcinoma
- Actinic keratosis or Bowen disease
- Keratoacanthoma
- Amelanotic melanoma
- Common wart or chronic infectious ulcer (e.g. cutaneous leishmaniasis in endemic areas)
Goal of treatment
Remove the tumour completely, treat precursor lesions, identify high-risk tumours and nodal spread early, and preserve function and appearance.
Treatment
- Surgical
- Surgical excision with clear margins is the standard treatment; Mohs micrographic surgery for high-risk tumours or tissue-sparing sites.
- Procedure
- Cryotherapy for actinic keratoses; curettage and electrodesiccation for small low-risk lesions; radiotherapy when surgery is not possible or after surgery for high-risk features.
- Medical
- Field therapy for actinic keratoses with topical fluorouracil, imiquimod or photodynamic therapy; immune checkpoint inhibitors (anti-PD-1) for advanced or metastatic disease.
- Surgical
- Neck or regional lymph-node dissection when nodes are involved.
- Follow-up
- Regular skin and lymph-node examinations, more frequent in transplant recipients and others with immunosuppression.
Complications
- Regional lymph-node metastasis
- Perineural spread along cranial nerves
- Local recurrence
- Distant metastasis (uncommon)
- Disfigurement after extensive tumours
Prognosis
Most tumours are cured by complete excision. The outlook worsens with high-risk features, nodal metastasis and immunosuppression; metastatic disease now often responds to immunotherapy.
Prevention
- Sun protection from childhood and avoiding tanning beds
- Treating actinic keratoses
- Skin checks in transplant recipients and outdoor workers
Test yourself
Think of the answer, then tap the question to see it.
Which precancerous lesion is the main precursor of cutaneous squamous cell carcinoma?
Actinic keratosis, a rough, scaly patch on chronically sun-exposed skin.
What is a Marjolin ulcer?
A squamous cell carcinoma arising in a chronic wound or old burn scar.
Which patient group has a markedly increased risk of cutaneous squamous cell carcinoma?
Organ-transplant recipients and other people with immunosuppression.
How does squamous cell carcinoma differ from basal cell carcinoma in behaviour?
It metastasises to regional lymph nodes more often, especially from the lip and ear, whereas basal cell carcinoma almost never spreads.
Related conditions
Educational information, not medical advice. For any symptom, see a health professional.
Sources: Squamous cell skin cancer (MedlinePlus, US National Library of Medicine, 2026).
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