Basal cell carcinoma

Overview

BCC is the most common cancer in the UK (~75-80% of skin cancers), arising from basal keratinocytes via PTCH1/hedgehog pathway dysregulation. Metastasis is exceedingly rare (<0.1%). Head and neck account for ~80% of cases.

Risk factors

•Chronic UV-B exposure - primary driver; fair skin, outdoor work, age >60
•Gorlin syndrome (naevoid BCC syndrome) - autosomal dominant PTCH1 germline mutation; multiple BCCs before age 30, jaw keratocysts, bifid ribs, falx cerebri calcification, medulloblastoma
•Immunosuppression (e.g. renal transplant recipients)

Presentation

BCC subtypes - key clinical features
SubtypeAppearanceKey point
NodularPearly/translucent papule, rolled everted edge, telangiectasia, central ulceration ('rodent ulcer')Most common subtype
SuperficialErythematous scaly plaque with thread-like raised borderCan mimic eczema/psoriasis - check border
MorphoeicPale, scar-like, indurated plaque with no clear borderMost dangerous to miss - margins far wider than visible lesion
PigmentedBlue-black/brown pigmentation within nodular lesionCan mimic melanoma
⚠️
Morphoeic BCC masquerades as a scar. Biopsy any persistent scar-like facial lesion without a clear history of injury.

Investigations

•Clinical examination - pearly edge, telangiectasia, rolled border often sufficient in experienced hands
•Dermoscopy - arborising (tree-like) telangiectasia, blue-grey ovoid nests, leaf-like structures, spoke-wheel areas; highly specific for BCC

🏆 Gold standard

•punch or shave biopsy with histology - confirms diagnosis, establishes subtype, assesses perineural invasion and margins; essential before treating morphoeic or recurrent BCC

Management

Stratify into low-risk vs high-risk before selecting treatment.

Low-risk vs high-risk BCC
FeatureLow-riskHigh-risk
SubtypeNodular or superficialMorphoeic
MarginsWell-definedIll-defined
LesionPrimaryRecurrent
Size/site<20 mm trunk/limbs or <6 mm faceLarge, periorbital/periauricular/perinasal/lip
OtherNo perineural invasion, immunocompetentPerineural/perivascular invasion, immunosuppressed
•First-line (low-risk nodular): surgical excision with 3-4 mm margin - recurrence <2%
•First-line (low-risk superficial, surgery not appropriate): imiquimod 5% cream (5 days/week for 6 weeks) or fluorouracil (5-FU) 5% cream
•Photodynamic therapy (PDT) - superficial or small nodular BCC on cosmetically sensitive areas
•Second-line / high-risk: Mohs micrographic surgery - morphoeic, recurrent, large, poorly defined, or critical sites (eyelid, nose, ear, lip); cure rate >99% primary, >94% recurrent
•Radiotherapy - patients unfit for surgery or significant functional impairment; also adjuvant after incomplete excision
•Curettage and electrodessication - small, low-risk, primary, non-facial BCC; no histological margin assessment
•Third-line (locally advanced/metastatic): vismodegib 150 mg oral once daily (hedgehog pathway inhibitor, SMO antagonist); also used in Gorlin syndrome
•Sonidegib - second SMO inhibitor, alternative to vismodegib for locally advanced BCC
🚨
Incomplete excision requires MDT discussion - re-excision (preferred), Mohs surgery, or adjuvant radiotherapy. Do not observe: recurrence risk is substantially higher and recurrent BCCs are far harder to treat.

Follow-up

•35-50% of patients develop a second primary BCC within 5 years
•Low-risk, completely excised: review at 3-6 months; no further routine follow-up if clear margins
•High-risk or incompletely excised: annual dermatology review for at least 5 years
•Gorlin syndrome and immunosuppressed: lifelong dermatology surveillance

Prognosis and complications

•5-year cure rate >98% for primary nodular BCC with clear margins; Mohs >99%
•Metastasis <0.1% - regional lymph nodes, lung, bone; median survival 8-14 months; hedgehog inhibitors improve outcomes
•Perineural invasion - tracks along cranial nerve branches; causes paraesthesia/pain; associated with recurrence
•Local tissue destruction - periorbital BCC can invade orbit; perinasal BCC can invade cartilage and bone