Basal cell carcinoma !
Basal cell carcinoma is the most common skin cancer. It grows slowly on sun-exposed skin, mostly the face, and rarely spreads, but it can destroy tissue.
Updated 2026-11-01
Structures involved
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In the clinical exam
Why it happens
- Tumour suppressor genes: RB, TP53, APC, BRCA and the two-hit hypothesis
- Radiation and cancer: ultraviolet and ionizing
- Biopsy: excisional, incisional, core needle, punch and fine-needle aspiration
- Ionizing radiation injury
- Frozen section: the intraoperative consultation
- Benign vs malignant tumours: the comparison table
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What it is
A slow-growing malignant tumour arising from the basal layer of the epidermis and hair follicles, usually on sun-exposed skin of the head and neck. It is locally invasive but almost never metastasises.
Who gets it
The most frequent cancer in fair-skinned populations and the most common skin cancer in Colombia. High-altitude Andean cities receive intense UV radiation all year, and outdoor workers such as farmers are at particular risk. Mostly seen after middle age.
Causes
- Cumulative and intermittent ultraviolet exposure
- Mutations in the Hedgehog signalling pathway (PTCH1, SMO)
- Ionising radiation and chronic arsenic exposure (less common)
Risk factors
- Fair skin, light eyes and tendency to burn
- Long-term outdoor work or recreation and high-altitude sun
- Older age and male sex
- Previous basal cell carcinoma
- Immunosuppression (e.g. organ transplant)
- Inherited syndromes such as basal cell naevus (Gorlin) syndrome and xeroderma pigmentosum
Pathophysiology
UV-induced mutations switch on the Hedgehog pathway in basal keratinocytes, which proliferate in nests with a characteristic palisading edge. The tumour depends on its surrounding stroma, which partly explains why it rarely metastasises, but it invades locally and can erode cartilage, bone and orbit if neglected.
Classification
- Nodular: the classic pearly papule with telangiectasias, sometimes with a central ulcer (rodent ulcer)
- Superficial: a scaly pink patch, often on the trunk
- Morpheaform (sclerosing): a scar-like plaque with ill-defined borders, aggressive
- Pigmented: contains melanin and can mimic melanoma
- Low-risk versus high-risk by site (central face, eyelids, nose, ears), size, subtype and recurrence
Symptoms and signs
- A pearly or translucent papule with rolled borders and fine surface vessels (telangiectasias)
- A sore that bleeds, crusts and does not heal, or heals and reopens
- A scaly pink patch on the trunk
- A whitish, scar-like area without previous injury
- Usually painless and slowly growing over months to years
Diagnosis
- Clinical
- Typical appearance on examination of sun-exposed skin; dermoscopy shows arborising vessels and other characteristic patterns.
- Tests
- Skin biopsy (shave or punch) confirms the diagnosis and the histological subtype.
- Imaging
- Not usually needed; CT or MRI when deep invasion of bone, orbit or nerves is suspected.
Differential diagnosis
- Cutaneous squamous cell carcinoma
- Amelanotic or pigmented melanoma
- Sebaceous hyperplasia or intradermal naevus
- Actinic keratosis or Bowen disease (for superficial lesions)
- Keratoacanthoma
Goal of treatment
Remove the tumour completely while preserving function and appearance, especially on the face, and detect new tumours early.
Treatment
- Surgical
- Standard surgical excision with clear margins is the usual treatment.
- Surgical
- Mohs micrographic surgery, with margin checks during the operation, for high-risk or recurrent tumours and for sites where tissue must be spared (nose, eyelids, ears).
- Procedure
- Curettage and electrodesiccation or cryotherapy for small, low-risk superficial lesions; radiotherapy for patients who cannot have surgery.
- Medical
- Topical immune-response modifiers (imiquimod) or topical fluorouracil for superficial types; Hedgehog pathway inhibitors for locally advanced or rare metastatic disease.
- Follow-up
- Periodic full skin examinations, since new skin cancers are common after a first one.
Complications
- Local tissue destruction and disfigurement
- Invasion of cartilage, bone or the orbit when neglected
- Recurrence after incomplete removal
- New primary skin cancers
- Metastasis (very rare)
Prognosis
Excellent: most tumours are cured by complete removal. Risk of recurrence is higher for large, central-face, morpheaform or previously treated tumours, and about half of patients develop another skin cancer within a few years.
Prevention
- Year-round sun protection, which matters at high altitude
- Avoiding tanning beds
- Regular skin checks in people with a previous skin cancer
Test yourself
Think of the answer, then tap the question to see it.
What is the most common skin cancer?
Basal cell carcinoma.
What is the classic appearance of nodular basal cell carcinoma?
A pearly, translucent papule with rolled borders and telangiectasias, sometimes with central ulceration (rodent ulcer).
Which signalling pathway is characteristically mutated in basal cell carcinoma?
The Hedgehog pathway (PTCH1 or SMO mutations).
When is Mohs micrographic surgery preferred?
For high-risk, recurrent or ill-defined tumours and in sites where tissue must be spared, such as the nose, eyelids and ears.
Related conditions
Educational information, not medical advice. For any symptom, see a health professional.
Sources: Basal cell skin cancer (MedlinePlus, US National Library of Medicine, 2026).
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