What is basal cell carcinoma?
Basal cell carcinoma (BCC) is a common, locally invasive, keratinocyte cancer (also known as nonmelanoma cancer). It is the most common form of skin cancer. BCC is also known as rodent ulcer and basalioma. Patients with BCC often develop multiple primary tumours over time.
Who gets basal cell carcinoma?
Risk factors for BCC include:
- Age and sex: BCCs are particularly prevalent in elderly males. However, they also affect females and younger adults
- Previous BCC or other form of skin cancer (squamous cell carcinoma, melanoma)
- Sun damage (photoageing, actinic keratoses)
- Repeated prior episodes of sunburn
- Fair skin, blue eyes and blond or red hair— note; BCC can also affect darker skin types
- Previous cutaneous injury, thermal burn, disease (eg cutaneous lupus, sebaceous naevus)
- Inherited syndromes: BCC is a particular problem for families with basal cell naevus syndrome (Gorlin syndrome), Bazex-Dupré-Christol syndrome, Rombo syndrome, Oley syndrome and xeroderma pigmentosum
- Other risk factors include ionising radiation, exposure to arsenic, and immune suppression due to disease or medicines
What causes basal cell carcinoma?
The cause of BCC is multifactorial.
- Most often, there are DNA mutations in the patched (PTCH) tumour suppressor gene, part of hedgehog signalling pathway
- These may be triggered by exposure to ultraviolet radiation
- Various spontaneous and inherited gene defects predispose to BCC
What are the clinical features of basal cell carcinoma?
BCC is a locally invasive skin tumour. The main characteristics are:
- Slowly growing plaque or nodule
- Skin coloured, pink or pigmented
- Varies in size from a few millimetres to several centimetres in diameter
- Spontaneous bleeding or ulceration
BCC is very rarely a threat to life. A tiny proportion of BCCs grow rapidly, invade deeply, and/or metastasise to local lymph nodes.
Complications of basal cell carcinoma
Recurrence of BCC after initial treatment is not uncommon. Characteristics of recurrent BCC often include:
- Incomplete excision or narrow margins at primary excision
- Morphoeic, micronodular, and infiltrative subtypes
- Location on head and neck
Recurrent basal cell carcinoma After PDT After superficial surgery After fluorouracil After imiquimod
Advanced BCCs are large, often neglected tumours.
- They may be several centimetres in diameter
- They may be deeply infiltrating into tissues below the skin
- They are difficult or impossible to treat surgically
How is basal cell carcinoma diagnosed?
BCC is diagnosed clinically by the presence of a slowly enlarging skin lesion with typical appearance. The diagnosis and histological subtype is usually confirmed pathologically by a diagnostic biopsy or following excision. Some typical superficial BCCs on trunk and limbs are clinically diagnosed and have non-surgical treatment without histology.
What is the treatment for primary basal cell carcinoma?
The treatment for a BCC depends on its type, size and location, the number to be treated, patient factors, and the preference or expertise of the doctor. Most BCCs are treated surgically. Long-term follow-up is recommended to check for new lesions and recurrence; the latter may be unnecessary if histology has reported wide clear margins.
Excision means the lesion is cut out and the skin stitched up.
- Most appropriate treatment for nodular, infiltrative and morphoeic BCCs
- Should include 3 to 5 mm margin of normal skin around the tumour
- Very large lesions may require flap or skin graft to repair the defect
- Pathologist will report deep and lateral margins
- Further surgery is recommended for lesions that are incompletely excised
Mohs micrographically controlled excision
Mohs micrographically controlled surgery involves examining carefully marked excised tissue under the microscope, layer by layer, to ensure complete excision.
- Very high cure rates achieved by trained Mohs surgeons
- Used in high-risk areas of the face around eyes, lips and nose
- Suitable for ill-defined, morphoeic, infiltrative and recurrent subtypes
- Large defects are repaired by flap or skin graft
Superficial skin surgery
Superficial skin surgery comprises shave, curettage, and electrocautery. It is a rapid technique using local anaesthesia and does not require sutures.
- Suitable for small, well-defined nodular or superficial BCCs
- Lesions are usually located on trunk or limbs
- Wound is left open to heal by secondary intention
- Moist wound dressings lead to healing within a few weeks
- Eventual scar quality variable
Cryotherapy is the treatment of a superficial skin lesion by freezing it, usually with liquid nitrogen.
- Suitable for small superficial BCCs on covered areas of trunk and limbs
- Best avoided for BCCs on head and neck, and distal to knees
- Double freeze-thaw technique
- Results in a blister that crusts over and heals within several weeks.
- Leaves permanent white mark
Imiquimod is an immune response modifier.
- Best used for superficial BCCs less than 2 cm diameter
- Applied three to five times each week, for 6–16 weeks
- Results in a variable inflammatory reaction, maximal at three weeks
- Minimal scarring is usual
5-Fluorouracil cream is a topical cytotoxic agent.
- Used to treat small superficial basal cell carcinomas
- Requires prolonged course, eg twice daily for 6–12 weeks
- Causes inflammatory reaction
- Has high recurrence rates
Radiotherapy or X-ray treatment can be used to treat primary BCCs or as adjunctive treatment if margins are incomplete.
- Mainly used if surgery is not suitable
- Best avoided in young patients and in genetic conditions predisposing to skin cancer
- Best cosmetic results achieved using multiple fractions
- Typically, patient attends once-weekly for several weeks
- Causes inflammatory reaction followed by scar
- Risk of radiodermatitis, late recurrence, and new tumours
What is the treatment for advanced or metastatic basal cell carcinoma?
Locally advanced primary, recurrent or metastatic BCC requires multidisciplinary consultation. Often a combination of treatments is used.
- Targeted therapy
Targeted therapy refers to the hedgehog signalling pathway inhibitors, vismodegib and sonidegib. These drugs have some important risks and side effects.
How can basal cell carcinoma be prevented?
The most important way to prevent BCC is to avoid sunburn. This is especially important in childhood and early life. Fair skinned individuals and those with a personal or family history of BCC should protect their skin from sun exposure daily, year-round and lifelong.
- Stay indoors or under the shade in the middle of the day
- Wear covering clothing
- Apply high protection factor SPF50+ broad-spectrum sunscreens generously to exposed skin if outdoors
- Avoid indoor tanning (sun beds, solaria)
Oral nicotinamide (vitamin B3) in a dose of 500 mg twice daily may reduce the number and severity of BCCs.
What is the outlook for basal cell carcinoma?
Most BCCs are cured by treatment. Cure is most likely if treatment is undertaken when the lesion is small.
About 50% of people with BCC develop a second one within 3 years of the first. They are also at increased risk of other skin cancers, especially melanoma. Regular self-skin examinations and long-term annual skin checks by an experienced health professional are recommended.