Summary

Basal Cell Carcinoma (BCC) is the most common skin cancer and the most common malignancy in humans overall. It arises from basal keratinocytes in the epidermis and is almost always caused by cumulative UV sun exposure. BCC is locally invasive but, crucially, almost NEVER metastasises (<0.1%). This makes it highly curable if detected and treated appropriately. However, if neglected, BCC can cause significant local destruction ("rodent ulcer"), particularly on the face. Management depends on subtype, location, and patient factors, ranging from simple excision to Mohs micrographic surgery for high-risk lesions.

Key Facts

• Commonest Cancer: ~75% of all skin cancers. ~150,000/year in UK.
• Metastasis Rate: <0.1%. Cure is the norm.
• Cause: Cumulative UV exposure (UVB primarily).
• Classic Appearance: Pearly/translucent nodule with rolled edge, telangiectasia. +/- Central ulceration (Rodent Ulcer).
• Subtypes: Nodular (most common), Superficial, Morphoeic/Infiltrative (aggressive).
• Treatment: Surgical excision (4mm margin standard). Mohs surgery for high-risk sites. Topical/ablative for superficial.
• Key Guideline: NICE CSG8 / BAD Guidelines on Skin Cancer.

Clinical Pearls

"The H-Zone": The central face (around Eyes, Nose, Lips, Ears, Temples) is high-risk. BCCs here require careful management (often Mohs) due to complex anatomy and risk of incomplete excision.

"If it bleeds, crusts, and never heals": This is the classic patient description of a BCC. Any skin lesion that repeatedly crusts and bleeds without fully healing should raise suspicion.

Morphoeic = Malignant Scar: The morphoeic subtype looks like a scar (flat, white, waxy). It has indistinct borders and is often much larger subclinically than it appears. Always think of it if a "scar" appears without a history of trauma.

Hedgehog Pathway: BCC is driven by aberrant activation of the Hedgehog signalling pathway (PTCH1, SMO genes). This is the target for oral drugs like Vismodegib in advanced BCC.

Why This Matters Clinically

While BCC is rarely life-threatening, it is incredibly common. Every clinician will encounter it. Recognising the subtypes and understanding which lesions need specialist referral (vs. GP excision) is essential. Inappropriate management of morphoeic or H-zone BCCs can lead to incomplete excision and recurrence, requiring more complex surgery later.

Dermoscopy Findings

Differential Diagnosis

After excising the BCC, we are left with a defect. The "Reconstructive Ladder" applies.

1. Secondary Intention (Heal by itself). Good for concave surfaces (inner canthus, conchal bowl). Poor for convex surfaces (nose tip).
2. Direct Closure. Ellipse. Orientation along Relaxed Skin Tension Lines (RSTLs).
3. Skin Graft. Full Thickness (FTSG) preferred for face (better colour match). Donor: Pre/Post-auricular, Supraclavicular.
4. Local Flaps. The workhorse of facial reconstruction.

Common Facial Flaps

• Transposition Flaps: The Bilobed Flap (Zitelli).
  • Indication: Distal nose defect <1.5cm.
  • Concept: Borrow skin from the lax upper nose to fill the tight lower nose.
• Advancement Flaps: The cheek advancement.
  • Indication: Large cheek defects.
• Rotation Flaps: The Rieger Flap (Dorsal Nasal Flap).
  • Indication: Large dorsal nasal defects.
• Interpolation Flaps: The Paramedian Forehead Flap.
  • Indication: Large defects of the nasal tip/ala (>1.5cm).
  • Concept: Forehead skin is the best match for nose skin. Requires 2 stages (pedicle division at 3 weeks).

The H-Zone Danger

• Reconstruction vs Surveillance:
  • Using a flap hides the deep margin.
  • If your excision wasn't complete, you have buried the tumour under a flap.
  • Rule: Never put a flap over a high-risk tumour unless margins are confirmed clear (Frozen section or Mohs).
  • If no frozen section available, use a Skin Graft or Secondary Intention first.

Mohs Micrographic Surgery (The Process)

1. Debulking: Visible tumour removed.
2. Layer 1: A thin disc of tissue (1-2mm) is removed including the whole margin.
3. Mapping: Tissue is cut into quadrants, colour-coded, and mapped to a diagram.
4. Freezing: Tissue froze and sectioned horizontally (en face).
5. Microscopy: Surgeon examines 100% of the peripheral and deep margin.
6. Targeted Re-excision: If tumour found at "3 o'clock", surgeon goes back ONLY to 3 o'clock.
7. Reconstruction: Once clear, the hole is repaired.

Surgical Excision

Mohs Micrographic Surgery

The gold standard for high-risk BCC.

Topical Treatments (Superficial BCC only)

Curettage & Cautery (C&C)

• Indication: Small, low-risk, superficial or nodular BCCs.
• Technique: Scrape tumour with curette, cauterise base. Repeat 2-3 times.
• Cure Rate: ~90% for appropriate lesions.
• Cosmesis: Leaves flat, hypopigmented scar.

Hedgehog Pathway Inhibitors

The Hedgehog Pathway (Deep Dive)

The discovery of the Hedgehog (Hh) pathway revolutionised our understanding of BCC.

• Normal State:
  • PTCH1 (Patched) is the receptor. It inhibits SMO (Smoothened).
  • With SMO inhibited, the pathway is OFF. No cell division.
• Ligand Binding:
  • Sonic Hedgehog (SHH) ligand binds to PTCH1.
  • Binding stops PTCH1 from inhibiting SMO.
  • SMO becomes active -> Activates GLI transcription factors -> Cell Division.
• In BCC:
  • Mutation: PTCH1 is broken (loss of function).
  • It cannot inhibit SMO.
  • SMO is permanently ON.
  • Cell divides uncontrollably.
• Treatment: Vismodegib binds to SMO and turns it off. It is a "SMO Inhibitor".

Adnexal Tumours (The Mimics)

BCC arises from the "folliculo-sebaceous-apocrine germ". Many benign tumours also arrive here and look like BCCs.

1. Trichoepithelioma: Benign hair follicle tumour. Flesh coloured papules on nasolabial folds. Multiple in "Brooke-Spiegler Syndrome". Can look exactly like BCC histologically (but no retraction artefact).
2. Sebaceous Hyperplasia: Yellowish papules with central dell. "Mature" sebocytes. Benign.
3. Microcystic Adnexal Carcinoma (MAC): Very dangerous. Looks like a benign lump but invades nerves aggressively. Needs Mohs.

Facial surgery leaves scars. A poor scar can be devastating.

The Process of Maturation

• 0-6 Weeks: Red, lumpy, immature. Sutures out at day 5-7 to prevent "railroading".
• 6 Weeks - 6 Months: Scar remodels. Collagen aligns.
• 12-18 Months: Final maturation (Pale, flat).

Interventions

1. Silicone Gel/Sheets: Gold standard. Hydrates the scar, reduces fibroblast activity.
2. Massage: Breaking down adhesions. Desensitisation.
3. Sun Protection: Fresh scars hyper-pigment permanently if sunburnt. Factor 50 is mandatory for 1 year.
4. Steroid Injection (Triamcinolone): For hypertrophic/keloid scars.

The SINS Trial (Surgery vs Imiquimod for Nodular & Superficial)

• Findings: Surgery is superior to Imiquimod.
• Recurrence: 2% (Surgery) vs 17% (Imiquimod) at 5 years.
• Cosmesis: Better in Imiquimod group.
• Conclusion: Trade-off. If you want a cure -> Surgery. If you want no scar and accept risk -> Cream.

The M-BCC Study (Morphoeic BCC)

• Confirmed that morphoeic BCCs extend subclinically far beyond visible margins.
• Standard 4mm excision often inadequate.
• Mohs recommended.

(As per original - restored)

What is a BCC?

A Basal Cell Carcinoma (BCC) is a type of skin cancer. It's the most common type and is almost always caused by sun damage over many years. The good news is that BCCs almost never spread to other parts of the body. They grow slowly and are very treatable.

What does it look like?

Often a shiny, pearly lump or a sore that won't heal. It may crust, bleed, and then seem to get a bit better, but never fully heals.

How is it treated?

Usually, it is removed with a small operation under local anaesthetic. For BCCs in difficult areas (like around the eyes or nose), a specialist surgery called Mohs can be used to make sure all the cancer is removed while saving as much healthy skin as possible.

Will it come back?

If completely removed, it is unlikely to come back at the same spot. However, having one BCC means you are at higher risk of getting another somewhere else on your skin in the future.

How can I prevent more?

• Sun protection: Sunscreen (SPF 30+), hats, protective clothing.
• Regular skin checks: Check your skin and see your GP if you notice any new or changing spots.