Basal Cell Carcinoma
Summary
Basal cell carcinoma (BCC) is the most common cancer in humans, accounting for 75-80% of all skin cancers. BCCs arise from basal keratinocytes in the epidermis and are strongly associated with cumulative UV exposure. They are locally invasive but rarely metastasise (<0.1%). The classic appearance is a pearly pink nodule with a rolled edge, telangiectasia, and central ulceration ("rodent ulcer"). Management depends on subtype, size, site, and patient factors. Surgical excision with 4mm margins is the gold standard. Mohs micrographic surgery offers tissue-sparing removal for high-risk facial lesions.
Key Facts
- Incidence: 200+ per 100,000 (most common cancer)
- Risk Factor: Cumulative UV exposure, fair skin, immunosuppression
- Appearance: Pearly nodule, rolled edge, telangiectasia
- Subtypes: Nodular (60%), Superficial (25%), Morphoeic (5-10%)
- Metastasis: <0.1% (essentially never)
- Treatment: Surgical excision (4mm margin), Mohs for high-risk facial
Clinical Pearls
"BCCs Don't Kill, But They Disfigure": Untreated, BCCs keep growing and invade locally. Near the eye or nose, this can be devastating. Early treatment = better cosmetic outcome.
"Rolled Edge is the Clue": The classic pearly rolled edge with telangiectasia is nearly pathognomonic. If you see it, it's BCC until proven otherwise.
"Morphoeic is Sneaky": Morphoeic (sclerosing) BCCs look like scars and extend beyond visible margins. These need Mohs surgery or wide excision.
"Previous BCC = More BCCs Coming": 40% get another BCC within 5 years. Annual skin surveillance is essential.
Incidence
- Most common human malignancy
- 200+ per 100,000 per year (UK)
- Incidence rising 3-5% annually
- Lifetime risk: 1 in 5-6 (Caucasians)
Demographics
- Peak age: 60-80 years (but occurring younger)
- M > F slightly
- Very rare in dark-skinned individuals
Risk Factors
| Factor | Risk |
|---|---|
| Cumulative UV exposure | Major |
| Fair skin, red/blonde hair | High |
| Freckling tendency | High |
| Outdoor occupation | High |
| Immunosuppression | 10-15x |
| Prior BCC | 40% get another within 5 years |
| Radiotherapy field | Increased |
| Gorlin syndrome | Multiple BCCs |
Site Distribution
- 80% head and neck
- Nose most common (30%)
- Less common on trunk/limbs (superficial subtype)
Origin
- Arises from basal layer of epidermis
- Also thought to arise from hair follicle stem cells
UV-Induced Carcinogenesis
- UV-B causes DNA damage (pyrimidine dimers)
- Mutations in tumour suppressor genes (PTCH1, p53)
- Hedgehog signalling pathway dysregulation
- Uncontrolled basal cell proliferation
Hedgehog Pathway
- PTCH1 normally inhibits Smoothened (SMO)
- PTCH1 mutation → SMO activation → Cell proliferation
- Target for vismodegib (advanced/metastatic BCC)
Why BCCs Rarely Metastasise
- Require stromal support
- Stromal dependency prevents distant spread
- <0.1% metastasis rate
Symptoms
BCC Subtypes
| Subtype | Frequency | Appearance | Behaviour |
|---|---|---|---|
| Nodular | 60% | Pearly nodule, telangiectasia, rolled edge, central ulcer | Most common, well-defined |
| Superficial | 25% | Erythematous scaly patch, fine thread-like edge | Often trunk, multiple |
| Morphoeic | 5-10% | Scar-like, waxy, ill-defined | Aggressive, infiltrative |
| Pigmented | 5% | Nodular with brown/black pigment | May mimic melanoma |
High-Risk Features
| Feature | Significance |
|---|---|
| Morphoeic/infiltrative subtype | Ill-defined margins, subclinical extension |
| Size >cm | Higher recurrence |
| Site: "H-zone" of face | Nose, periorbital, periauricular, lip |
| Recurrent tumour | More aggressive |
| Immunosuppression | Higher recurrence |
| Perineural invasion | Spreads along nerves |
Inspection
- Pearly/translucent papule or nodule
- Rolled (raised) edge
- Telangiectasia (small blood vessels) on surface
- Central depression or ulceration
- Crust/scab that recurs
Dermoscopy Findings
- Arborising vessels (branching)
- Ulceration
- Blue-grey ovoid nests
- Shiny white structures
- Absence of pigment network (vs melanoma)
Palpation
- Usually firm
- Morphoeic: May feel indurated beyond visible margins
Diagnosis
- Clinical diagnosis in typical cases
- Dermoscopy: Aids diagnosis, distinguishes from other lesions
- Biopsy: If diagnosis uncertain or pre-treatment planning
- Punch biopsy or incisional biopsy
- Shave biopsy acceptable for superficial BCC
Histopathology
- Basaloid cells with peripheral palisading
- Clefting between tumour and stroma
- Subtype determination
Imaging
- Usually not required
- CT/MRI if suspecting bone invasion or perineural spread
Treatment Options Summary
| Treatment | Best For | Cure Rate |
|---|---|---|
| Surgical excision | Most BCCs | >5% |
| Mohs surgery | High-risk facial, morphoeic, recurrent | >9% |
| Curettage & electrodessication | Small, low-risk, superficial | 90-95% |
| Topical imiquimod | Superficial BCC only | 80-85% |
| Photodynamic therapy (PDT) | Superficial BCC | 85-90% |
| Radiotherapy | Elderly, non-surgical candidates | 90-95% |
Surgical Excision
┌──────────────────────────────────────────────────────────┐
│ SURGICAL EXCISION OF BCC │
├──────────────────────────────────────────────────────────┤
│ MARGINS: │
│ • Well-defined nodular: 4mm peripheral margin │
│ • Ill-defined/morphoeic: 6-13mm OR Mohs │
│ • Deep margin: Down to subcutaneous fat minimum │
│ │
│ RECONSTRUCTION: │
│ • Direct closure if possible │
│ • Flap/graft for larger defects │
└──────────────────────────────────────────────────────────┘
Mohs Micrographic Surgery
- Tissue-sparing, staged excision
- 100% margin examination
- Highest cure rate (>99%)
- Indications:
- High-risk facial sites (periorbital, nasal, periauricular)
- Morphoeic/infiltrative subtype
- Recurrent BCC
- Large tumours
- Immunosuppressed patients
Non-Surgical Options
| Treatment | Protocol | Indications |
|---|---|---|
| Imiquimod 5% | Once daily 5x/week for 6 weeks | Superficial BCC only |
| PDT | Two treatments 7 days apart | Superficial BCC, larger areas |
| Radiotherapy | Fractionated course | Non-surgical candidates, adjuvant |
Advanced/Metastatic BCC
- Hedgehog pathway inhibitors: Vismodegib, Sonidegib
- Side effects: Muscle spasms, alopecia, dysgeusia, weight loss
- Reserved for locally advanced unresectable or very rare metastatic BCC
Of BCC
- Local invasion
- Destruction of local structures (nose, eye, ear)
- Perineural spread
- Recurrence
- Very rarely metastasis (<0.1%)
Of Treatment
- Surgical: Scarring, infection, nerve damage
- Mohs: Time-consuming, requires specialist
- Imiquimod: Intense local inflammation
- PDT: Pain during treatment, photosensitivity
Cure Rates
| Treatment | Cure Rate (Primary BCC) |
|---|---|
| Mohs surgery | 99% |
| Surgical excision (adequate margins) | 95-98% |
| Curettage | 90-95% |
| Radiotherapy | 90-95% |
| Imiquimod (superficial) | 80-85% |
Recurrence Risk Factors
- Incomplete excision (positive margins)
- Morphoeic/infiltrative subtype
- Large tumour
- High-risk site
- Previous recurrence
Follow-Up
- Annual skin check (40% develop another BCC)
- Patient education on sun protection
- Self-examination
Key Guidelines
- BAD Guidelines for BCC (2021): bad.org.uk
- NICE Skin Cancers Referral Pathway
- NCCN Guidelines: Basal Cell Skin Cancer
Key Evidence
Mohs vs Excision
- RCT (2004): 10-year recurrence Mohs 4.4% vs excision 12.2% for recurrent BCC
- For primary: Similar outcomes
Imiquimod for Superficial BCC
- 5-year clearance: 80-85%
- Efficacy inferior to surgery but acceptable for appropriate cases
What is Basal Cell Carcinoma?
Basal cell carcinoma (BCC) is the most common type of skin cancer. It's caused mainly by sun exposure over many years. The good news is that it grows very slowly and almost never spreads to other parts of the body. However, if left untreated, it can get larger and damage surrounding skin and tissues.
What Does it Look Like?
BCCs often appear as:
- A shiny pink or pearly bump
- A sore that bleeds, scabs over, and then returns
- A flat, skin-coloured or brown lesion that looks like a scar
- A pink/red patch that might itch
They most commonly appear on sun-exposed areas like the face, ears, and neck.
How is it Treated?
Most BCCs are treated with a simple surgical procedure to cut out the cancer with a margin of normal skin. For BCCs in tricky areas like near the eye or nose, a special technique called Mohs surgery may be used - this removes the cancer layer by layer to preserve as much healthy skin as possible.
Some superficial BCCs can be treated with creams or light therapy.
Can I Prevent BCC?
Yes! Protecting yourself from UV radiation helps:
- Use sunscreen SPF 30+ daily
- Wear protective clothing and a hat
- Avoid midday sun (10am-4pm)
- Don't use sunbeds
- Have regular skin checks if you've had BCC before
Primary Guidelines
- British Association of Dermatologists. BAD Guidelines for the Management of Basal Cell Carcinoma. 2021.
- NCCN Guidelines. Basal Cell Skin Cancer. Version 2.2024.
Key Studies
- Mosterd K, et al. Surgical excision versus Mohs micrographic surgery for basal-cell carcinoma of the face: randomised controlled trial. Lancet. 2008;371(9627):1833-37. PMID: 18503818
- Bath-Hextall FJ, et al. Interventions for basal cell carcinoma of the skin. Cochrane Database Syst Rev. 2007. PMID: 17253520