• Mountain View Vet Surgery

You find a skin lump on your pet. What you do next is important.

Updated: Nov 19, 2018

Many skin lumps are harmless, but some aren't so it pays to get them checked. If the more serious ones are treated early, we can dramatically change the outcomes for your pet. Today we are talking about cutaneous mast cell tumours.

How to identify a Mast Cell Tumour at home. If you apply pressure or force to a small skin tumour, and it instantly blows up like a severe insect bite reaction, and 24 hours later it is back to it's previous size, you have found a mast cell tumour. There was only one visible tumour (big one at the bottom) before we shaved this dog's leg, but the clippers caused others to release histamine and "blow up". We confirm the diagnosis by taking a fine needle aspiration for staining and microscopy. These are one of the most common skin tumours we diagnose.

Take the first Step

Has your dog developed an unexpected lump? To investigate, we take a fine needle aspirate from the tumour and can often get an instant diagnosis in house with our Diff Quik stain system and microscopy. Below is an aspirate we took from a dog. It is a mast cell tumour, one of the more common (and potentially nasty tumours) that we find. Complex samples are sent to a local Veterinary Pathology Service for Diagnostics. On some occasions we need to remove a mass to get a diagnosis and the fine needle aspirate may be inconclusive, even after evaluation by a pathologist.

Mast cell tumor. Mast cell tumors are usually distinguished by numerous round cells with distinct purple granules.

What happens next?

Mast cell tumours should be surgically excised whenever possible, while some are benign, others are very aggressive tumours, and there is no way of knowing what we are dealing with until the whole tumour is examined by a trained histopathologist. Surgery is by wide excision as these tumours have often spread away from the visible lump - this means drawing a 2cm margin around the tumour then resecting along that line and resecting one additional layer of tissue beneath the tumour.

These three photographs above show the surgical process involved in removing a solitary mast cell tumour from the hind leg of a Staffy. The tumour was resected along the ink lines, then a plastic surgery procedure was used to close the large deficit without excess tension. The third photograph is 14 days after surgery showing excellent healing.

We follow up these patients every 3 months for any evidence of the appearance of new tumours. Many of these patients go on to develop further tumours. The Staffy and Boxer breeds are over-represented in patients presenting with these tumours.


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