What is a squamous cell carcinoma of the skin?
Squamous cell carcinoma (spinocellular carcinoma) is a malignant tumour of the skin. Unlike basal cell carcinoma, squamous cell carcinoma is able to spread (metastasise) to the rest of the body. This usually only happens once the original tumour has reached a fairly large size. Squamous cell carcinoma can also invade cartilage or bone lying beneath the skin tumour.
How does it look?
Squamous cell carcinoma often begins as a small, wart-like area of thickened, scaly skin (hyperkeratosis), especially on skin that has been heavily exposed to the sun. Particularly in the early stage, a squamous cell carcinoma can look very similar to an actinic keratosis or Bowen’s disease. Actinic keratoses are generally regarded as precursors of squamous cell carcinoma.
At first the squamous cell carcinoma is painless, but when the tumour is about 1 cm in size, pain can develop. Over time an ulcer may form within the tumour. If not treated adequately, a squamous cell carcinoma can grow to several centimetres in size, and the chance of tumour cells spreading is increased with such large tumours. Typical of squamous cell carcinomas are the crusty, scaly elements, although not all of them show this hyperkeratosis.
Who gets it?
Squamous cell carcinoma of the skin is seen mainly on sun-exposed skin in people with a fair skin type. The tumour occurs about twice as often in men as in women. It is much more common in fair-skinned populations living in sunny countries such as Australia. Squamous cell carcinomas not infrequently occur in the context of chronic actinic (sun) skin damage.
How does it develop?
Several factors influence the development of squamous cell carcinoma:
- Heredity / skin type. People with a fair skin type (who burn easily) have a greater chance of developing squamous cell carcinoma. Because of the lack of pigment, the genetic material in the cell nucleus (DNA) is insufficiently protected against the harmful effects of ultraviolet light. DNA damage, and the resulting disturbance of cell division, is the consequence.
- Sun exposure. The more exposure to the sun, the greater the chance of developing squamous cell carcinoma.
- Reduced immunity. Squamous cell carcinomas are seen more often in people with reduced immunity. An important risk group is people who have had an organ transplant and take medicines to prevent organ rejection. The first squamous cell carcinomas often begin to appear after 5 to 10 years. Being very careful with sun exposure can considerably delay the development of these tumours.
Special forms of squamous cell carcinoma
A few fairly rare forms deserve separate mention:
- Penile carcinoma — seen mainly in men between 40 and 70 years of age. It is much rarer in circumcised men, and better hygiene is thought to play a role in prevention. Penile carcinoma is particularly aggressive.
- Vulval carcinoma — squamous cell carcinoma of the vulva is seen mainly in older women, and is often found in skin affected by lichen sclerosus of the vulva. It too tends to spread quickly, so timely recognition is important.
Unlike ordinary squamous cell carcinoma, sunlight plays no significant role in penile and vulval carcinoma.
How is squamous cell carcinoma treated?
When a dermatologist suspects a squamous cell carcinoma, a small sample of the tissue is usually taken first (a biopsy) for examination by a pathologist. If the diagnosis is confirmed, the tumour is removed surgically. After this procedure, regular outpatient checks of the scar, the lymph nodes and the rest of the skin follow, the latter to detect any new squamous cell carcinomas in good time.
What is the outlook?
As noted, squamous cell carcinoma of the skin can spread, particularly with rapidly growing, aggressive tumours. Fortunately, metastasis is uncommon: of 100 patients with squamous cell carcinomas treated adequately, about one will develop metastases. It is essential that the skin is subsequently protected well against sunlight, to prevent extra ultraviolet damage and thereby new tumours.
When to see a doctor
See a doctor for any rough, scaly, wart-like or crusted spot that grows, becomes tender, ulcerates or does not heal — especially on sun-exposed skin — so that it can be examined and, if needed, treated early.