Squamous Cell Carcinomas

A squamous cell carcinoma – that sounds at first like a distant medical term, but for dog owners it can suddenly become very real. It is a malignant tumour arising from the outer layers of skin or mucous membranes. Locally, it grows aggressively and destroys surrounding tissue, but metastasises to other body regions comparatively late.

This tumour most frequently appears in dogs on sun-exposed areas of the skin – or in the mouth, or on the paw pads. Dogs with light-coloured skin and little protective fur on their belly and ears are particularly at risk.

Symptoms and identifying features

Rule of thumb: A lump or a wound that stubbornly fails to heal after two weeks requires a vet visit. Do not wait, do not hope.

On the skin, crusty, bleeding ulcers are often visible – preferably on the nose, ears or belly. In the mouth, swelling of the gums stands out, often accompanied by bad breath and difficulty eating. Some dogs suddenly drool more or stubbornly refuse their favourite treat, which they previously chewed without problems. This is a signal that should be taken seriously.

On the toes, the tumour manifests as persistent lameness and noticeable swelling. In addition, the nail may change colour or even fall off – which owners understandably often mistake for an injury and therefore wait too long.

Which dogs get squamous cell carcinomas more frequently?

Dalmatians, Beagles and Boxers carry a certain genetic predisposition for this type of tumour.

However, UV exposure over many years is even more decisive. Dogs with white fur and light skin that lie in the sun for long hours every day carry a significantly increased risk – compared to darkly pigmented animals, the difference is considerable.

Chronic irritation also plays a role. If you smoke at home, you expose your dog to a measurable additional risk. The same applies to regular contact with chemicals – this sounds like an exception, but it is certainly relevant in some professional environments involving dogs.

How does the vet diagnose the carcinoma?

Better safe than sorry: The definitive diagnosis is provided only by a tissue sample under the microscope. No blood count, no palpation can replace that.

The vet takes a biopsy from the suspicious area – usually under anaesthesia. For oral tumours, X-rays are added so that it can be assessed whether the tumour has already grown into the jawbone.

For tumours in the nose, a CT scan is necessary. The central question there: How far has the tumour advanced towards the base of the skull? This fundamentally influences therapy planning.

What treatment options are available?

Standard therapy is surgical removal with a generous safety margin from healthy tissue.

In skin carcinomas, about one centimetre of healthy tissue around the tumour is often removed. This reduces the recurrence rate to approximately 15% – in other words: In 85% of cases, the tumour remains gone permanently.

Oral tumours are more demanding. Sometimes part of the jaw must be removed – that sounds drastic, but most dogs eat surprisingly well again after healing.

Radiation therapy comes into play when the tumour is difficult to access, for example deep in the nose. The treatment usually takes three weeks with daily sessions.

Chemotherapy, on the other hand, plays hardly any role – squamous cell carcinomas respond poorly to it. It is practically only used when the tumour has already metastasised.

What are the chances of recovery?

Early-detected skin carcinomas have a survival rate of over 90%. Those are good figures – if you act in time.

Oral carcinomas are significantly more difficult: About 60% of affected dogs survive the first year after diagnosis. That is precisely why early detection makes a big difference here.

Toe carcinomas lie in between, provided the tumour can be completely removed. Often, amputation of the affected toe is the only sensible approach – but the quality of life of the dogs suffers surprisingly little from this. Most walk quite normally afterwards.

Prevention

In at-risk dogs, sun protection is the most important measure – and the simplest one.

Owners of light-coloured dogs should avoid the harsh midday sun and apply sunscreen to the nose and ears if necessary. Important here: it is better to use special dog sunscreen than products for humans – the latter may contain ingredients that are not harmless for dogs.

And if you smoke: In dogs, an increased risk of nasal and paranasal sinus tumours is proven, especially in long-nosed breeds (Reif et al. 1998), as well as lung and bladder tumours. For oral tumours in dogs, this evidence is still lacking – so far, only genetic damage in the oral mucosa has been proven. In cats, however, the link between passive smoking and oral squamous cell carcinoma is described. A smoke-free household therefore protects not only the people in it.