What is a basal cell carcinoma?
Basal cell carcinoma is the most common form of cancer in humans, and it is becoming more common. Roughly one in five people will develop one or more basal cell carcinomas during their lifetime. It usually arises on parts of the skin that are frequently exposed to the sun. This form of skin cancer is very treatable: it (almost) never spreads to other parts of the body and is therefore rarely life-threatening.
Which types of basal cell carcinoma are there?
Several types can be distinguished:
- Nodular basal cell carcinoma (the most common) — a glassy, skin-coloured papule, often with small blood vessels visible within it (telangiectasia). Larger examples often have a small central crater. It generally grows slowly.
- Infiltrative (“strand-like”) basal cell carcinoma — often looks like the nodular type, but the border between the tumour and normal skin is frequently hard to make out. It is called “strand-like” because it forms small extensions into the skin.
- Superficial basal cell carcinoma — grows very superficially in the skin and can strongly resemble a patch of eczema. This common form is described in a separate article.
- Trunk-skin carcinoma — also a superficial basal cell carcinoma, seen mainly on the trunk. Its relationship with sun exposure is less clear than in other types.
- Sclerosing / morphoea-type basal cell carcinoma — usually resembles scar tissue and may lie slightly sunken into the skin.
Who develops it?
People with a fair skin type (skin type 1 or 2) have the greatest risk of developing basal cell carcinomas after a lot of sun exposure. In the past these tumours were seen mainly in older people; nowadays they occur increasingly in younger people, sometimes from the age of 30, because of increased sun exposure — for example during holidays in (sub-)tropical destinations. It is therefore not surprising that basal cell carcinomas are found mainly on sun-exposed skin such as the face, ears and neck. They are often seen as part of chronic sun damage to the skin.
Basal cell carcinoma is also seen in people with basal cell naevus syndrome, a very rare inherited condition in which people develop basal cell carcinomas at a young age. When young people develop multiple basal cell carcinomas, this condition is always investigated; this usually includes careful inspection of the skin and X-rays of the jaws (which may contain cysts).
How is it treated?
There are several treatment options. The choice depends on the type of basal cell carcinoma, its size and its location on the body.
Surgery
Surgery is the “gold standard” treatment. Advantages: the removed tumour can be examined by the pathologist, so it is known whether the tumour has been completely removed; the scar usually heals quickly; and it is a relatively minor procedure. Disadvantage: large tumours sometimes require large and complex operations.
Forms of surgery:
- Oval (elliptical) excision — the tumour is removed under local anaesthetic. An oval piece of skin is taken so the wound can be closed neatly, always with a margin of a few millimetres to be sure the whole tumour is removed. The wound edges are then brought together and stitched. Performed by dermatologists and (plastic) surgeons.
- Transpositions (local flaps) — when an oval excision is not possible (for example because there is too little “give” in the skin to bring the edges together), nearby skin can be slid or rotated into the defect. Many types are possible, depending on the site and size. Performed by dermatologists and plastic surgeons.
- Skin grafts — for some very large basal cell carcinomas the skin cannot be closed normally, and a skin graft follows. For grafts on the face, skin from behind the ear is often used as donor skin because its structure most resembles facial skin. Performed by plastic surgeons.
- Mohs micrographic surgery — especially for infiltrative basal cell carcinomas in important sites such as the corners of the eye or the nose, it is vital to be certain the tumour is completely removed. Because a wide “safety” margin cannot be taken there, this special technique is used: during the operation the pathologist examines the tissue and tells the surgeon whether the tumour is completely removed, and if not, exactly which edge still contains tumour. The surgeon then removes only a further strip of skin at that spot. Several “rounds” may be needed; only when tissue examination shows the tumour has gone is the skin closed. This gives maximum certainty of complete removal while sparing as much healthy skin as possible.
Radiotherapy
Some basal cell carcinomas are well suited to radiotherapy. Advantage: often a good cosmetic result. Disadvantages: afterwards it is not 100% certain the tumour has completely gone, because no pathology examination is possible to confirm complete removal; and treatment takes place in multiple sessions, on average about 18 sessions spread over several weeks.
Curettage, cautery and freezing
- Curettage and cautery — the tumour is scraped from the skin with a sharp metal spoon, and the base is then burned to stop bleeding and remove any remnants. The drawback is that it is not known whether removal was complete. This is generally regarded as an older technique, but in very specific cases there may be reason to use it.
- Freezing (cryotherapy) — the tumour is frozen with special equipment, typically for about two cycles of 20 seconds. Again, no statement can be made about completeness of removal, and there is a weeping wound for some weeks. Even so, especially for superficial basal cell carcinomas, freezing can be a good alternative to surgical removal.
Creams and light-based treatments (mainly for superficial tumours)
- 5-fluorouracil cream — suitable for superficial basal cell carcinomas. This chemotherapy cream is usually applied twice a day for about 4 weeks. The tumour cells die and a superficial wound is left that heals by itself (sometimes supported with an antibiotic ointment). It avoids surgery and a surgical scar, but gives no certainty about completeness of removal.
- Photodynamic therapy — a cream containing a “photoactive” substance (methyl aminolevulinate or 5-aminolevulinic acid) is applied to the tumour and taken up fairly selectively by the tumour cells. The area is then illuminated with red light of a specific wavelength, which triggers a reaction that destroys the tumour cells. Here too, completeness of removal cannot be confirmed by a pathologist.
- Imiquimod cream — a relatively new treatment for superficial basal cell carcinoma. The cream is applied to the tumour 5 times a week and washed off after 8 hours; total treatment lasts about 6 weeks.
Follow-up after removal
After a basal cell carcinoma has been removed, a number of check-ups always follow. The scar is inspected and the skin is checked for new basal cell carcinomas. In the first year you are usually checked twice, and once a year thereafter, often being discharged from follow-up after about 5 years.
How can new basal cell carcinomas be prevented?
Having developed a basal cell carcinoma is usually a sign that the skin has already had a lot of sun damage. It is therefore important to protect the skin well from strong sun to prevent further damage. A good sunscreen, protective clothing (a hat!) and avoiding strong sun at the hottest times of day (in summer between about 11:00 and 16:00) are essential.
When to see a doctor
Have any new, slowly growing, glassy or pearly bump, a non-healing sore that keeps crusting and bleeding, or an eczema-like patch that does not respond to usual treatment, checked by a doctor or dermatologist.