What is basal cell carcinoma?

Basal cell carcinoma is a malignant tumour of basaloid keratinocytes arising from cells of the basal layer of the epidermis or hair follicle outer root sheath. Despite the 'cancer' label its behaviour is generally indolent — local growth without metastasis is the rule, and patients typically die with rather than of BCC. The clinical challenge is preventing local destruction of important structures (eye, nose, ear) and avoiding unnecessary recurrence.

Who gets BCC?

BCC is the most common malignancy in white populations. UK incidence exceeds 100,000 cases per year; NCRAS historically undercounts because only the first BCC per patient is registered. Lifetime risk is approximately 1 in 5 in Fitzpatrick I–II skin and rises with age. Most UK BCCs occur on the head and neck (~70%), trunk (~20%), and limbs.

Risk factors

☀Cumulative UVGreater contribution than intermittent UV (cf. melanoma).
IFitzpatrick I–IIFair skin, freckling, blue eyes, red/blonde hair.
⊘ImmunosuppressionOTRs, CLL, biologics, prolonged corticosteroids.
☢Prior radiotherapyLatency 10–30 years; field of radiotherapy.
⚛ArsenicHistoric exposure; well-water, occupational.
GGorlin syndromePTCH1 / SUFU — multiple BCCs from young age.
XXeroderma pigmentosumDNA-repair deficiency; very early-onset multiple BCCs.
●Previous BCC25–50% chance of further BCC within 3 years.

Histological subtypes

The WHO / BAD classification distinguishes low-risk from high-risk histological subtypes — central to margin choice and surgical planning.

Low-risk subtypes

**Nodular BCC** — pearly papule, telangiectasia, rolled border, frequently with central erosion.

Superficial BCC, trunk — **Superficial BCC** — pink/red macule or thin plaque on the trunk; multiple in sun-damaged skin.

**Pigmented BCC** — nodular or superficial with melanin; differential includes melanoma.

High-risk subtypes

Morphoeic BCC, cheek — **Morphoeic (sclerosing)** — scar-like, ill-defined; subclinical spread; high recurrence.

Infiltrative BCC — **Infiltrative** — aggressive deep extension, poorly defined borders.

Dermoscopy

Dermoscopy is highly accurate for BCC diagnosis when classical features are present. See the dermoscopy reference.

Dermoscopic features (≥1, plus absence of melanocytic structures)

Arborising vessels — large-calibre, branching tree-like vessels in sharp focus on the surface (pathognomonic).
Blue-grey ovoid nests — large blue-grey confluent areas (pigmented BCC).
Blue-grey globules — multiple smaller pigment globules.
Leaf-like (maple-leaf) areas — discrete brown-grey peripheral bulbous extensions.
Spoke-wheel structures — radial projections meeting at a darker hub.
Concentric structures — newer recognised criterion.
Ulceration — central erosion, often with adherent serum.
Shiny white structures — chrysalis-like, polarised only.
Absence of pigment network — important negative criterion.

Diagnosis

Diagnosis is clinical, supported by dermoscopy. Histological confirmation is usually obtained by incisional or punch biopsy (4 mm) for ill-defined or large lesions, or directly by excisional biopsy where the diagnosis is clinically clear and the lesion is small / well-defined.

For superficial BCC suspected on the trunk, a shave or punch biopsy may suffice to confirm subtype before committing to topical therapy versus excision.

Clinical pearlThe H-zone

The embryonic fusion planes of the face — medial canthus, nasolabial fold, pre- and post-auricular areas — are 'H-zone' sites where BCC has a higher risk of subclinical extension. Plan for Mohs or staged excision with paraffin-embedded margin assessment for high-risk H-zone BCC.

The facial H-zone — The facial 'H-zone' — central face, periocular, nasolabial folds, ears — where Mohs is preferred.

Differential diagnosis

●Intradermal naevusSoft, fleshy, often hairs; no pearliness or telangiectasia.
●Sebaceous hyperplasiaYellow lobular papule with crown vessels; central dell.
●Trichoepithelioma / fibrofolliculomaMultiple in genetic syndromes; biopsy distinguishes.
●Squamous cell carcinomaHyperkeratotic, faster growing, induration.
●Amelanotic melanomaPink nodule; pink melanoma trap.
●Bowen's diseaseErythematous scaly plaque; glomerular vessels on dermoscopy.
●Molluscum contagiosumUmbilicated dome; multiple in immunosuppressed.
●Scar / morphoeaMimic of morphoeic BCC; biopsy if any doubt.

Management

Guideline UK national guidance Trial randomised trial NICE TA NICE Technology Appraisal Consensus expert opinion Local MDT MDT-dependent Full key →

Guideline Surgery (first line for most)

Risk	Peripheral margin
Low-risk (small, well-defined nodular / superficial; trunk / limbs)	4 mm
High-risk (morphoeic, infiltrative, micronodular, basosquamous, recurrent, H-zone, >2 cm, immunosuppressed)	5–10 mm or Mohs

Excision should be planned with primary closure or local flap reconstruction in mind. Site-specific reconstruction is covered in the reconstruction atlas.

BCC excision marking, nasolabial fold — BCC excision marking — peripheral margin and ellipse orientation along nasolabial fold to optimise scar.

Mohs micrographic surgery

See the Mohs surgery technique reference. Indicated for:

H-zone BCC.
Recurrent BCC.
BCC >2 cm.
Morphoeic, infiltrative, micronodular, basosquamous histology.
Poorly defined clinical borders.
Where maximum tissue sparing matters (eyelid, nasal ala, helix).

Non-surgical options

CCurettage & cauterySmall, well-defined, low-risk BCC on trunk or limbs; not for H-zone.
❄CryotherapySmall superficial BCC, palliative settings.
RxTopical imiquimod or 5-FUSuperficial BCC; counsel about lower cure rates than surgery.
⌬MAL-PDTSuperficial BCC and some thin nodular; field treatment option.
☢RadiotherapyWhen surgery unsuitable. Avoid in Gorlin syndrome.
℞Vismodegib Local MDT Locally advanced / metastatic BCC unsuitable for surgery / RT. NICE TA489 did not recommend routine NHS use; not routinely NHS-commissioned, so confirm any funding route through specialist MDT / IFR processes before use.

UK practiceMDT referral

All high-risk BCC, recurrent BCC, and BCC requiring reconstruction beyond primary closure should be discussed at the local skin cancer specialist MDT per NHS IOG for skin cancer services.

Complications

Local recurrence (especially morphoeic, infiltrative, recurrent, incompletely excised).
Cosmetic and functional morbidity from advanced or repeatedly recurrent disease.
Locally advanced (laBCC) — destruction of vital structures (eye, nose, dura).
Metastasis (very rare; predominantly basosquamous; lung, bone).
Hedgehog inhibitor side effects: dysgeusia, alopecia, muscle cramps, weight loss, teratogenicity.

Follow-up

Routine follow-up is not recommended for single, completely excised low-risk BCC (BAD 2021); patients should be educated on self-examination and sun protection.

Adequately treated isolated BCC: no routine hospital follow-up, except postoperative review where appropriate; discharge with written histology result, safety-netting and patient-initiated re-access instructions.
High-risk BCC with residual recurrence concern: discuss at MDT; if observation or conservative monitoring is chosen, 6-monthly review in year 1, then annual review for at least 5 years, with longer follow-up for selected high-risk patients.
Incompletely excised high-risk: re-excise or Mohs where possible; do not default to watch-and-wait without MDT rationale.
Multiple BCCs / Gorlin syndrome: at least yearly follow-up if further tumours or recurrence are likely within 12 months; Gorlin usually requires lifelong personalised dermatology surveillance.
Immunosuppressed (OTR, CLL): individualise frequency by tumour burden and keratinocyte cancer risk, with field control.

Prognosis

BCC has an excellent prognosis with appropriate treatment — disease-specific mortality is <0.1%. The major morbidity is cosmetic and functional from local destruction or repeated surgery. Recurrence rates after surgical excision are 1–10% depending on subtype and margin; Mohs reduces recurrence to 1–3% even for high-risk lesions. Patients with one BCC carry a 25–50% 3-year risk of a further BCC.

Basal cell carcinoma