‘IT is only a tiny, wee, soft lump and it has been there for ages, so it can’t be nasty, can it?’

It’s an impossible question to answer, even when the offending mass is right there in front of your eyes.

This dog owner, like many others, had sensibly sought reassurance that her gut feeling was correct. And most times it would be.

Many dogs have lumps and bumps that are totally benign and cosmetic rather than medical issues.

But some are not.

Amongst the worst of these, and the most common malignant skin tumour in dogs, is the Mast Cell Tumour. Accounting for one fifth of skin cancers, these appear mainly on the trunk, perineum and legs and, unfortunately, don’t look like anything in particular. Indeed, one of my colleagues refers to them as ‘the masters of disguise’.

They are generally described as ‘hard to soft, in the skin or under the skin’. And that about sums them up.

Unlike sebaceous cysts or epitheliomas or even melanomas, mast cell tumours cannot reliably be diagnosed by inspection alone.

Of course, there are times that they are suspected.

They are more often seen in dogs over eight years old and some breeds (Boxers, Bostons, Weimeraners, Labradors, Staffies, Beagles and Pugs) are predisposed.

Mast cells release histamine when aggravated, causing localised swelling and inflammation, so any lesion that appears to fluctuate in size or any mass that suddenly looks angry and starts to weep should be investigated quickly.

Excisional surgery may be delayed until a fine needle aspirate of the lesion has been sent to the lab to confirm the diagnosis and, for obvious reasons, ulcerated lumps should be treated with kid gloves to avoid further damage.

There are various degrees of malignancy of mast cell tumours. Some can be cured by surgical removal. The most severe grade, however, can spread rapidly and life expectancy is reduced. Ideally, wide excision is advised, so that around 3-5cm beyond the lump is removed, but this is rarely possible in practice and often the edges of the tumour, by its very nature, are not well defined.

Problems with wound closure can occur, mainly due to a shortage of available skin, making subsequent breakdown a risk.

A recent medical treatment, however, may be more of a breakthrough. A new biologically active chemical called tigilanol tiglate, found in the seed of the Australian native blushwood plant (Fontainea picrosperma) can be injected into mast cell tumours with remarkable results.

Seventy five per cent of growths are removed with a single injection, with changes seen in the mass within two hours. A second injection increases the success rate to 87.2 per cent. Happily, 88 per cent of treated dogs were disease free at twelve months. Of course, it’s not cheap.

So. Back to our tiny, wee, soft lump that had been there for ages. What do we do? It is not a precise science but you have to take its appearance, the breed, the age, the history and some experience into account. Then you have to guess and reach for a needle to actually find out. As ever, life is not so easy, despite our best attempts.