What is Basal Cell Carcinoma (BCC)? Causes, Symptoms and Treatment

What is basal cell carcinoma (BCC)?

Basal cell carcinoma (BCC) — also called basal cell skin cancer — develops from basal cells, which form the lowest layer of the epidermis. These cells sit just above the boundary with the dermis and are responsible for continuously renewing the skin's surface cells.

BCC typically grows slowly over months to years. It rarely spreads to other organs (metastasises), which distinguishes it from more aggressive forms of skin cancer such as melanoma and squamous cell carcinoma (SCC). However, if left untreated, BCC can grow deep into the skin and damage underlying structures such as bone and cartilage — especially on the face.

According to the International Classification of Diseases (ICD-11), BCC is classified as code 2C32 (Basal cell carcinoma of skin).

What does basal cell carcinoma look like?

BCC can appear in several different forms, and it is important to be aware of the most common presentations:

• Pearly nodule: The most classic form. A small, smooth bump with a pearly or waxy sheen and often visible tiny blood vessels (telangiectasias) on the surface.
• Flat, coloured patch: A flat, pink or red patch with slightly raised, rolled edges. May resemble an area of chronic eczema or a scab that does not heal.
• Scar-like area: A small, white or yellowish area resembling a scar, often with thin, shiny skin over it.
• Open sore: A sore that does not heal, bleeds easily or forms a crust, and returns after healing.

BCC most commonly appears on sun-exposed areas: the face (especially the nose), ears, neck, shoulders and upper arms.

Why does basal cell carcinoma occur?

The primary cause of BCC is chronic exposure to ultraviolet (UV) radiation from the sun or tanning beds. UV radiation damages the DNA in skin cells, and when this damage accumulates over time in basal cells, they can begin to grow uncontrollably and form a tumour.

The same accumulated UV damage produces actinic keratoses — rough, scaly patches on sun-exposed skin. They are a visible marker that the skin has taken enough UV radiation to raise the risk of skin cancer.

What are the main risk factors?

• Chronic sun exposure: Long-term, repeated sun exposure throughout life — especially during childhood and teenage years — is the most important risk factor. Accumulation of UV damage over time is key.
• Fair skin tone: People with fair skin, light eyes and blonde or red hair have less melanin pigment and therefore less natural protection against UV radiation.
• Age: BCC most commonly affects people over 50 years old, as UV damage accumulates over decades.
• Immune suppression: People with organ transplants, HIV or those taking immunosuppressant medications have an elevated risk.
• Previous BCC or family history: If you have had a BCC once, your risk of developing another is significantly elevated — around 40–50% of people develop a new one within five years. A first-degree relative with skin cancer also raises your risk, partly through shared genetics and partly through shared sun habits.
• Previous injuries: Scars, burns or chronic wounds on the skin can increase the risk in the affected area.

Who gets basal cell carcinoma?

BCC can in principle affect anyone, but certain groups are significantly more vulnerable:

• Older adults: Risk increases significantly after age 50, as UV damage has had decades to accumulate.
• People with fair skin: Celtic, Scandinavian or other Northern European background is associated with higher risk.
• People with high sun exposure: People who work outdoors or spend a lot of time in the sun have an increased risk.
• The immunocompromised: Organ transplant recipients have roughly a 10-fold higher risk of BCC than the general population — the far larger 65–100-fold increase applies to squamous cell carcinoma, not BCC. People living with HIV have a smaller increase, around twofold.

In Denmark, BCC affects roughly as many women as men. Danish register data give a male-to-female ratio of about 1:1.1 — that is, slightly more women than men. The pattern shifts with age: women predominate below 45, while men predominate in the older age groups. The difference is partly attributed to differences in sun exposure patterns and occupational environments.

How is basal cell carcinoma diagnosed?

With an in-person examination and, in practice, always a skin biopsy. The dermatologist first examines the lesion with a dermatoscope — a magnifying device with polarised light that reveals structures such as fine branching blood vessels and blue-grey nests of pigment that are invisible to the naked eye.

The definitive diagnosis, however, requires microscopy. A small sample of the lesion — or the whole lesion — is removed under local anaesthetic and examined under a microscope. This examination (histology) confirms that it is a BCC, establishes the subtype and shows how deeply it is growing. All of this determines which treatment is appropriate.

A photo assessment can tell you whether a lesion looks concerning enough to be seen in person, and how quickly. It cannot rule out skin cancer. A suspicious spot needs examination with a dermatoscope and, if there is any doubt, removal of the lesion for laboratory analysis.

What can you do about basal cell carcinoma?

The good news is that BCC is highly treatable — especially when detected early. Treatment options depend on the tumour's size, location, depth and your overall health:

How can you prevent basal cell carcinoma?

By limiting UV damage. Since BCC is primarily caused by the accumulation of UV damage over decades, the best protection starts early in life:

• Sunscreen year-round: Use broad-spectrum sunscreen with SPF 30 or higher every day — even on cloudy days and in winter. Apply 15–30 minutes before sun exposure and reapply every two hours.
• Avoid tanning beds: Tanning beds significantly increase the risk of skin cancer. There is no safe form of tanned skin from artificial radiation.
• Protective clothing and hats: Wear a wide-brimmed hat, sunglasses and tightly woven clothing. Seek shade during midday hours (12–3 pm), when UV radiation is strongest.
• Monthly self-examination: Check your skin from head to toe once a month. Watch for new bumps, spots or sores that do not heal within 4–6 weeks.
• Annual dermatologist check-up: Have a professional skin examination at least once a year — and more often if you are in a high-risk group.

Frequently asked questions